Cesarian Delivery and Autism – another inconvenient truth?

Brasil is the C-section capital of the world, with rates in the public sector of 35–45%, and 80–90% in the private sector.

A recent study from the Karolinska Institute in Sweden, analysing 61 previous studies, has again shown a connection between birth by Cesarian Section and an increased risk of autism or indeed ADHD. 

C-sections account for just 16% of births in Sweden, but 32% in North America.

This of course prompted a reaction to reassure future mothers that they have nothing to fear, from experts in obstetrics who of course know nothing about the etiology of autism.  Mothers should be reassured, but trashing the study helps nobody.  Instead of a 1% risk of non-trivial autism, it rises to 1.3%. You still have more than a 98% chance of having a neurotypical child, all other factors being equal.  Without a medically necessary C-section, death is a real possibility.

It was a couple of years ago that the Karolinska Institute highlighted the fact that those with severe autism currently have a life expectancy of under 40 years.  Another inconvenient truth.

Association of Cesarean Delivery With Risk of Neurodevelopmental and Psychiatric Disorders in the Offspring 

Question  Is birth by cesarean delivery associated with an increased risk of neurodevelopmental and psychiatric disorders in the offspring compared with birth by vaginal delivery?

Findings  In this systematic review and meta-analysis of 61 studies comprising more than 20 million deliveries, birth by cesarean delivery was significantly associated with autism spectrum disorder and attention-deficit/hyperactivity disorder.

Meaning  The findings suggest that understanding the potential mechanisms behind these associations is important, especially given the increase in cesarean delivery rates for nonmedical reasons.

Abstract

Importance  Birth by cesarean delivery is increasing globally, particularly cesarean deliveries without medical indication. Children born via cesarean delivery may have an increased risk of negative health outcomes, but the evidence for psychiatric disorders is incomplete. 

Conclusions and Relevance  The findings suggest that cesarean delivery births are associated with an increased risk of autism spectrum disorder and attention-deficit/hyperactivity disorder, irrespective of cesarean delivery modality, compared with vaginal delivery. Future studies on the mechanisms behind these associations appear to be warranted. 

Very many things are known to slightly increase the odds of a person having autism and the more risk factors you have the more severely autistic you may be.  This ranges from maternal stress (anything from experiencing a hurricane, work stress, life trauma) to maternal/paternal age, obesity, gestational diabetes, alcohol/drug abuse, illness during pregnancy etc. This combines with whatever is in the parents’ DNA and random mutations that are bound to occur.    

A more rational reaction might be to investigate further why there might be a link and how you could counter any risk to children born by cesarian section.  You only have to read the existing research, or this blog.

There are 2 very good reasons why there should be a link between autism and C section, both have been covered in this blog.

1.     The microbiome comes from the mother. Science is only recently starting to understand the role of bacteria in health, but we know that it plays a key role in conditioning/calibrating the immune system of babies.  Once the immune system has been calibrated it is set for life.  Early exposure to bacteria is necessary and humans evolved to expect it.  If your immune system is over/under sensitive there will be consequences. Birth via C-section avoids exposure to bacteria in the birth canal, unless the newly arrived baby is “seeded” with bacteria from the mother. Mother’s milk is another key source of transferring the mother’s microbiome to the baby. 

2.     We saw that the birthing hormone Oxytocin plays a key role in triggering the “GABA switch” in new-borns. This is the process which transforms immature neurons with high chloride to mature neurons with low chloride shortly after birth.  During natural birth there is a surge in the hormone Oxytocin that is transferred to the baby, this causes the chloride transporter KCC2 to be further expressed and the “opposing” transporter NKCC1 to fade away.  In many people with severe autism their neurons remain in the immature state their entire life.  Just as you can replace the bacteria transfer lost in birth via C-section, there would be absolutely no reason why you could not replicate the surge in Oxytocin to "flip the GABA switch".

The recent study showed that elective C-sections (where the baby is in perfect health and not distressed) are associated with the elevated risk of both Autism and ASD.

Regular readers of this blog would probably be surprised if C-section did not increase autism prevalence.

The important thing is to acknowledge this likely connection and mitigate it, rather than try and fault the numerous studies that have shown the same effect.

The same of course applies to reducing the very small risk from vaccines, rather than construct new studies in a contrived way to show there is zero risk.   If you can safely and cheaply reduce the risk of a negative reaction to vaccines, why wouldn’t you?  Just follow Johns Hopkins example and give Ibuprofen or Montelukast (Singular) for a few days before and after and remember to never give Paracetamol/Acetaminophen (Tylenol) in response to fever after a vaccine. Paracetamol/ Acetaminophen reduces the body’s key antioxidant GSH just when the baby/child may need its neuroprotection most.

Some conditions are associated with preterm births, a good example is Cerebral Palsy (CP), which is twice as common in babies born very early. CP is rarely genetic and is usually considered to be caused by a complication during pregnancy, birth or shortly thereafter. I think you would find a correlation between C-sections and CP, but in this case I doubt you would find it in elective C-sections.   In other words C-sections do not “cause” CP, but they may be associated with it. The ID/MR often found in CP might be elevated by C-section and, if so, would be treatable.

Conclusion

In order to halt the rise in incidence of the disabling kinds of autism there should be steps taken to reduce some of the very many factors that are driving the increase, albeit each one sometimes by a tiny amount.

This would be a good application of all those thousands of autism research papers, many of which have shown what factors contribute to increased risk, that now sit gathering dust.

We are not at the stage of wide scale gene editing, but many simple steps can be taken today to improve future health.  This does not mean do not vaccinate, or avoid medically necessary C-sections; vaccinations and C-sections have saved millions of lives. But, why would you not want to take a good thing and make it even better?  That is what we humans tend to be good at, like the Swedes and their Volvos.

Perhaps take your C-section with a generous smear of Mum's bacteria and a shot of synthetic oxytocin?  

There will be more on Cerebral Palsy in a later post on D-NAC (Dendrimer N-Acetyl Cysteine). 

                                                               

Cognitive Loss/Impaired Sensory Gating from HCN Channels - Recovered by PDE4 Inhibition or an α2A Receptor Agonist

Today we have a complex dysfunction, but we have a plausible understanding of the detailed biological underpinnings and several therapeutic options. It is relevant to people with autism who have impaired sensory gating (they find noises like a clock ticking annoying), and perhaps those who struggle with complex thought. It is very likely to be disturbed in some people with ADHD and many with schizophrenia.

Trouble in the Pre-Frontal Cortex

For a recap on sensory gating, here is an earlier post:-

Sensory Gating in Autism, Particularly Asperger's

Today’s dysfunction relates to HCN channels located on those tiny dendritic spines in a part of the brain called the pre-frontal cortex. These are a type of voltage gated potassium channel found in your brain and heart, there are 4 types, it looks to me that HCN2 is the key one today.

The pre-frontal cortex (PFC) is seen as the part of the brain most affected by mental illness (schizophrenia, bipolar, ADHD etc.), although medicine’s current understanding looks rather medieval to me.

These HCN channels can open when they are exposed to cAMP (cyclic adenosine monophosphate). When open, the information can no longer flow into the cell, and thus the network (created by numerous interacting neurons) is effectively disconnected.

By keeping these channels closed, it is thought that you can improve working memory and reducing distractibility. Now you might think distractibility is an odd word, and it is not a word I expected to encounter, what it really means is impaired sensory gating. This is a core feature of Asperger’s, ADHD and schizophrenia.

One of the key risk genes for schizophrenia, DISC1, also affects HCN channels and this may account for some of the cognitive deficit found in schizophrenia. High level thinking is particularly affected.  It is thought that loss of DISC1 function in the PFC would likely prevent proper PDE4 function, leading to a dysregulated build-up of cAMP in dendritic spines resulting in excessive opening of HCN channels

Role of disrupted in schizophrenia 1 (DISC1) in stress-induced prefrontal cognitive dysfunction

I did wonder how nicotine fits in, since in earlier post we saw that α7 nAChR agonists, like nicotine, improve sensory gating and indeed that people with schizophrenia tend to be smokers. It turns out that nicotine is also an HCN channel blocker. For a change, everything seems to fit nicely together. There are different ways to block HCN channels, some of which are indirect. One common ADHD drug, Guanfacine, keeps these channels closed, but in a surprising way.

Alpha-2A adrenergic receptors near the HCN channels, on those dendritic spines, inhibit the production of cAMP and the HCN channels stay closed, allowing the information to pass through into the cell, connecting the network. These Alpha-2A adrenergic  receptors are stimulated by a natural brain chemical norepinephrine, or by drugs like Guanfacine.

Stress appears to flood PFC neurons with cAMP, which opens HCN channels, temporarily disconnects networks, and impairs higher cognitive abilities.

This would explain why stress makes people’s sensory gating problems get worse. So someone with Asperger’s would get more distracted/disturbed at exam time at school for example, or when he goes for a job interview. Reducing stress is another method to improve sensory gating and indeed cognition. In Monty, aged 14 with ASD, the only time he exhibits significantly impaired sensory gating, is when he has stopped all his Polypill therapies for several days. I think stress/anxiety is what has changed and this opens those HCN channels. Then even the sound of someone eating food next to him makes him angry.

Excessive opening of HCN channels might underlie many lapses in higher cognitive function.

While the researchers at Yale patented the idea of HCN blockers to improve cognition, we can see how other existing ideas to improve cognition may indeed have the same mechanism, most notably PDE4 inhibitors.

The University of Maastricht holds patents on the use of Roflumilast, a PDE4 inhibitor, to improve cognition; most interestingly, this takes effect at one fifth of the COPD dosage, for which it is an approved drug. At high doses PDE4 inhibitors have annoying side effects, but at low doses they tend to be trouble-free.

One effect of a PDE4 inhibitor is that it reduces cAMP. So a PDE4 inhibitor acts indirectly like an HCN blocker.

Not surprisingly recent research showed that low doses of Roflumilast improves sensory gating in those affected by this issue.

So rather than waiting for a brain selective HCN blocker, the potential exists to use a one fifth dose of Roflumilast today. This is something that should indeed be investigated across different types of cognitive dysfunction.

There are numerous dysfunctions that can impair cognition and they can occur in different diagnosis. For example impaired autophagy is a key feature of Huntington’s, impaired remyelination defines multiple sclerosis, low levels of nerve growth factor are a key feature of Rett syndrome. Less severe dysfunctions of these processes occur in entirely different conditions.

It is thought that people with Alzheimer’s might benefit from PDE4 inhibition. If it was me, I would try it in all types of dementia or cognitive loss of any kind.

PDE4 Inhibitors

There have been many mentions of PDE4 inhibitors elsewhere in this blog. They are broadly anti-inflammatory and anti-oxidant, but currently only widely used to treat asthma in Japan and COPD in Western countries. COPD is a kind of very severe asthma.

Traditionally a PDE4 inhibitor is thought of as drug used to block the degradative action of phosphodiesterase 4 (PDE4) on cyclic adenosine monophosphate (cAMP). That all sound complicated, just think of it as increasing cAMP.

Now cAMP is a messenger in many biological processes, one of which relates to PKA (Protein Kinase A). In autism we know that PKA, PKB and PKC are often disturbed. These PKs are very important because they have the ability to literally change the function of thousands of proteins in your body. This is similar to how epigenetic tags can switch on or switch off a particular gene. PKs, via a different mechanism we will look at in another post, change the function of proteins, so it is very important that you have the correct level of PKA, PKB and PKC.

We saw in a recent post that the Pitt Hopkins gene TCF4 is regulated by PKA and that under-expression of TCF4 is also a feature of some ID and schizophrenia. So more PKA, please.

The Intellectual Disability and Schizophrenia Associated Transcription Factor TCF4 Is Regulated by Neuronal Activity and Protein Kinase A 

You can use a PDE4 inhibitor to increase cAMP, which then increases PKA.

Other effects of PDE4 inhibitors

Today’s post is about sensory gating and the effect here of PDE4 inhibitors is via the effect of cAMP on those HCN channels in your tiny dendritic spines.

There are numerous other effects of PDE4 that may also be therapeutic. One interesting effect is that inhibition of PDE4 can mimic calorie restriction by activating AMPK/SIRT1 pathway.

Calorie restriction has just been shown in a large trial to be able to reverse type 2 diabetes, if initiated with a few years of the disease developing.

Humans have evolved based to periods of feast and famine. Periods of fasting may be therapeutic for many modern conditions.

Not surprisingly one side effect of PDE4 inhibitors is weight loss. Many psychiatric drugs cause troubling weight gain.

Acute administration of Roflumilast enhances sensory gating in healthy young humans in a randomized trial. 

Abstract

 

INTRODUCTION:

Sensory gating is a process involved in early information processing which prevents overstimulation of higher cortical areas by filtering sensory information. Research has shown that the process of sensory gating is disrupted in patients suffering from clinical disorders including attention deficit hyper activity disorder, schizophrenia, and Alzheimer's disease. Phosphodiesterase (PDE) inhibitors have received an increased interest as a tool to improve cognitive performance in both animals and man, including sensory gating.

METHODS:

The current study investigated the effects of the PDE4 inhibitor Roflumilast in a sensory gating paradigm in 20 healthy young human volunteers (age range 18-30 years). We applied a placebo-controlled randomized cross-over design and tested three doses (100, 300, 1000 μg).

RESULTS:

Results show that Roflumilast improves sensory gating in healthy young human volunteers only at the 100-μg dose. The effective dose of 100 μg is five times lower than the clinically approved dose for the treatment of acute exacerbations in chronic obstructive pulmonary disease (COPD). No side-effects, such as nausea and emesis, were observed at this dose. This means Roflumilast shows a beneficial effect on gating at a dose that had no adverse effects reported following single-dose administration in the present study.

CONCLUSION:

The PDE4 inhibitor Roflumilast has a favourable side-effect profile at a cognitively effective dose and could be considered as a treatment in disorders affected by disrupted sensory gating.

Treating Cognitive Impairment with Roflumilast, Maastricht University

Background Information

Selective phosphodiesterase (PDE) inhibition has been considered as a very promising target for cognition enhancement.

Roflumilast is a PDE4 inhibitor that has been developed by Takeda for Chronic Obstructive Pulmonary Disease (COPD). In recent year, Maastricht University has been collaborating with Takeda to develop Roflumilast for cognitive impairments

In 2015 Takeda sold COPD indication of Roflumilast to AstraZeneca, and ownership of IP for treatment of cognitive impairment returned to Maastricht University.

Compelling clinical results

A single administration of Roflumilast improves episodic memory in mice, and in young and elderly healthy subjects at a non-emetic dose

As shown in the figure, healthy (A) and memory impaired (B) elderly subjects showed better performances in the delayed recall of the Verbal Learning Task after roflumilast

Key Features and Advantages

Opportunities to reposition a clinically-proven safe compound with a well-established pharmacology.

Compelling preclinical and clinical evidences showing that Roflumilast effectively deliver to the brain to produce robust cognitive enhancement.

Pro-cognitive effects at low dose (5 times lower than COPD indication), which allows to circumvent the emetic effects commonly observed with other PDE4 inhibitors

Maastricht University has a strong IP protection extending to at least 2033.

Effect of Roflumilast on cognitive function in schizophrenia

PDE inhibitors in psychiatry--future options for dementia, depression and schizophrenia?

Author information

Abstract

Phosphodiesterases are key enzymes in cellular signalling pathways. They degrade cyclic nucleotides and their inhibition via specific inhibitors offers unique 'receptor-independent' opportunities to modify cellular function. An increasing number of in vitro and animal model studies point to innovative treatment options in neurology and psychiatry. This review critiques a selection of recent studies and developments with a focus on dementia/neuroprotection, depression and schizophrenia. Despite increased interest among the clinical neurosciences, there are still no approved PDE inhibitors for clinical use in neurology or psychiatry. Adverse effects are a major impediment for clinical approval. It is therefore necessary to search for more specific inhibitors at the level of different PDE sub-families and isoforms.

Brain Networks Strengthened By Closing Ion Channels, Research Could Lead To ADHD Treatment

The current study found that brain cells in PFC contain ion channels called hyperpolarization-activated cyclic nucleotide-gated channels (HCN) that reside on dendritic spines, the tiny protrusions on neurons that are specialized for receiving information. These channels can open when they are exposed to cAMP (cyclic adenosine monophosphate). When open, the information can no longer flow into the cell, and thus the network is effectively disconnected. Arnsten said inhibiting cAMP closes the channels and allows the network to reconnect.

Guanfacine can strengthen the connectivity of these networks by keeping these channels closed, thus improving working memory and reducing distractibility," she said. "This is the first time we have observed the mechanism of action of a psychotropic medication in such depth, at the level of ion channels."

Arnsten said the excessive opening of HCN channels might underlie many lapses in higher cognitive function. Stress, for example, appears to flood PFC neurons with cAMP, which opens HCN channels, temporarily disconnects networks, and impairs higher cognitive abilities.

The study also found alpha-2A adrenergic receptors near the channels that inhibit the production of cAMP and allow the information to pass through into the cell, connecting the network. These receptors are stimulated by a natural brain chemical  norepinephrine or by medications like guanfacine.

 “Guanfacine can strengthen the connectivity of these networks by keeping these channels closed, thus improving working memory and reducing distractibility,” she said. “This is the first time we have observed the mechanism of action of a psychotropic medication in such depth, at the level of ion channels.”

Yale has submitted a patent application on the use of HCN blockers for the treatment of PFC cognitive deficits based on the data reported in the Cell paper.

The full Yale paper:

α2A-Adrenoceptors Strengthen Working Memory Networks by Inhibiting cAMP-HCN Channel Signaling in Prefrontal Cortex

Guanfacine for the Treatment of Cognitive Disorders: A Century of Discoveries at Yale

The prefrontal cortex (PFC) is among the most evolved brain regions, contributing to our highest order cognitive abilities. It regulates behavior, thought, and emotion using working memory. Many cognitive disorders involve impairments of the PFC. A century of discoveries at Yale Medical School has revealed the neurobiology of PFC cognitive functions, as well as the molecular needs of these circuits. This work has led to the identification of therapeutic targets to treat cognitive disorders. Recent research has found that the noradrenergic α2A agonist guanfacine can improve PFC function by strengthening PFC network connections via inhibition of cAMP-potassium channel signaling in postsynaptic spines. Guanfacine is now being used to treat a variety of PFC cognitive disorders, including Tourette’s Syndrome and Attention Deficit Hyperactivity Disorder (ADHD). This article reviews the history of Yale discoveries on the neurobiology of PFC working memory function and the identification of guanfacine for treating cognitive disorders.

Nicotine blocks the hyperpolarization-activated current Ih and severely impairs the oscillatory behavior of oriens-lacunosum moleculare interneurons.

Molecular modeling suggests that, similarly to ZD 7288, nicotine and epibatidine directly bind to the inner pore of the HCN channels. It is therefore likely that nicotine severely influences rhythmogenesis and high cognitive functions in smokers.

Modulation of HCN channels in lateral septum by nicotine

Conclusion

I think many people stand to benefit from the drugs mentioned in today’s post, but for different biological reasons. A person with Pitt Hopkins may benefit from Roflumilast because it will upregulate PKA and then increase expression of their remaining TCF4 gene.

In a person with schizophrenia there are multiple reasons these drugs might help them and it will depend on which genes they have that are misexpressed (TCF4, DISC1 etc.).

In a person with idiopathic Asperger’s and impaired sensory gating it looks like the effect on HCN channels is what is important.

I think low dose Roflumilast has great potential for many. The Japanese drug Ibudilast very likely will provide similar benefits, but at what dosage?

PDE4 inhibitors do have side effects at higher doses in part because there are several different types of PDE4 (PDE4A, PDE4B, PDE4C etc) and different drugs effect different subtypes differently.

Ibudilast is used as a daily drug therapy for asthma in Japan and is being studied as a therapy for Multiple Sclerosis (MS) in the US.

Roflumilast is sold by Astra Zeneca as Daxas/Daliresp but at a high dose of 500mcg to treat flare ups of COPD (Chronic Obstructive Pulmonary Disease) it does cause troubling side effects, but it reduces your chance of dying from COPD.

The cognitive dose used in research is 100mcg. Higher doses had no cognitive/sensory gating benefit.

Further investigation of the ADHD drug Guanfacine should be made, because some of the people who benefit from a PDE4 inhibitor might get a similar effect from Guanfacine. People with Pitt Hopkins would not be in this category. A person with Asperger’s and impaired sensory dating should respond to Guanfacine, a cheap drug.

At the end of the day, choice of therapy will come down to side effects and cost. In the US, Roflumilast is expensive ($330), seven times more expensive than in some other countries; in the UK the price of the same 30 tablets is $50. One pack would be enough for 5 months at the suggested dose.

Polygenic Disorders that Overlap – Autism(s), Schizophrenia(s), Bipolar(s) and ADHD(s) – Creativity & Intelligence

Blogs are inevitably rather jumbled up and lack a clear structure; today’s post really should be at the beginning.

One clear message from the more sophisticated research into neuropsychiatric disorders is that they are generally associated with variances in the expression of numerous different genes, making them polygenic.

What I find interesting is that there is a substantial overlap in the genes that are miss-expressed across different neuropsychiatric disorders.  This is further proof, if it was needed, that the observational diagnoses used by psychiatrists are rather primitive.

So individual people will have a near unique set of genetic variances that make their symptoms slightly different to everyone else.  However it is highly likely that discrete biological dysfunctions will exist across the diagnoses.  So for example elevated intracellular chloride will be found in some autism and some schizophrenia. A calcium channelopathy affecting Cav1.2 would be found in some autism and some bipolar.

Eventually you would dispose of the old observational diagnoses like bipolar and give the biological diagnoses.  Then you will have the same drugs being used in a person with “bipolar” and another with “autism”.  When all this will happen is no time soon. 

In the meantime people interested in autism can benefit from the research into the other neuropsychiatric disorders.  These other disorders can be much better researched, partly because they usually concern adults who are fully verbal and have typical IQ.  In many cases there are both hypo and hyper cases in these disorders.   

Also of interest is that the same unusual gene expression in schizophrenia/bipolar is linked to creativity and the autism genes to intelligence. This is put forward as an explanation as to why evolution has conserved rather than erased neuropsychiatric disorders.

Height is polygenic 

Let’s start will a simple example.

There is no single gene that determines your height. Some school books suggest 3 or 4 genes, so let’s assume that is correct for now.

Traits are polygenic when there is wide variation. For example, humans can be many different sizes. Height is a polygenic trait, controlled by at least three genes with six alleles. If you are dominant for all of the alleles for height, then you will be very tall. There is also a wide range of skin colour across people. Skin colour is also a polygenic trait, as are hair and eye colour.

Polygenic inheritance often results in a bell shaped curve when you analyze the population. Most people fall in the middle of the phenotypic range, such as average height, while very few people are at the extremes, such as very tall or very short. At one end of the curve will be individuals who are recessive for all the alleles (for example, aabbcc); at the other end will be individuals who are dominant for all the alleles (for example, AABBCC). Through the middle of the curve will be individuals who have a combination of dominant and recessive alleles (for example, AaBbCc or AaBBcc).

There may be 4 or 6 or more alleles involved in the phenotype. At the left extreme, individuals are completely dominant for all alleles, and at the right extreme, individuals are completely recessive for all alleles. Individuals in the middle have various combinations of recessive and dominant alleles.

Unfortunately the real world is a bit more complex than high school biology. 

Defining the role of common variation in the genomic and biological architecture of adult human height

“Our results indicate a genetic architecture for human height that is characterized by a very large but finite number (thousands) of causal variants.”

Genes vs the Environment 

The spectrum of human diseases are caused by a multitude of genetic and environmental factors acting together. In certain conditions such as Down syndrome , genetic factors predominate, while in infections for example, environmental factors predominate. Most chronic non-communicable conditions such as schizophrenia and diabetes as well as congenital malformations are caused by an interaction of both genetic and environmental factors.

Source: http://www.gfmer.ch/SRH-Course-2010/course-files/pdf/Multifactorial-polygenic-inheritance-Hamamy-2010.pdf

The environment and epigenetic change

Some environmental influences, like smoking or pollution, can also become genetic in that heritable epigenetic markers can become tagged to a specific gene.  This impacts whether it is turned on or off.  

Multifactorial vs Polygenic Inheritance 

Multifactorial inheritance diseases that show familial clustering but do not conform to any recognized pattern of single gene inheritance are termed multifactorial disorders. They are determined by the additive effects of many genes at different loci together with the effect of environmental factors.

These conditions show a definite familial tendency but the incidence in close relatives of affected individuals is usually around 2-4%, instead of the much higher figures that would be seen if these conditions were caused by mutations in single genes (25-50%).

Examples of disorders of multifactorial inheritance

·        asthma

·        schizophrenia

·        diabetes mellitus

·        hypertension

Polygenic inheritance involves the inheritance and expression of a phenotype being determined by many genes at different loci, with each gene exerting a small additive effect. Additive implies that the effects of the genes are cumulative, i.e. no one gene is dominant or recessive to another.

According to the liability/threshold model, all of the factors which influence the development of a multifactorial disorder, whether genetic or environmental, can be considered as a single entity known as liability.

The liabilities of all individuals in a population form a continuous variable, which can be exemplified by a bell shaped curve.

Individuals on the right side of the threshold line represent those affected by the disorder. 

In autism the threshold keeps being moved, because the definition of the disease keeps being widened.

Liability curves of affected and their relatives

The liability curve is relevant to the question posed by parents who have autism in the family and want to know whether it will occur again and also to grown up siblings of those with autism.

The curve for relatives of affected will be shifted to the right; so the familial incidence is higher than the general population incidence.

So the biggest future autism risk is likely to be a previous occurance. 

There are ways to actively promote protective factors and shift the curve back to the left; but a risk will remain. 

Evidence that Autism is Polygenic 

This is a paper from 2016 that looks at how the genetic risks are additive.

Polygenic transmission disequilibrium confirms that common and rare variation act additively to create risk for autism spectrum disorders 

Autism spectrum disorder (ASD) risk is influenced by both common polygenic and de novo variation. The purpose of this analysis was to clarify the influence of common polygenic risk for ASDs and to identify subgroups of cases, including those with strong acting de novo variants, in which different types of polygenic risk are relevant. To do so, we extend the transmission disequilibrium approach to encompass polygenic risk scores, and introduce with polygenic transmission disequilibrium test. Using data from more than 6,400 children with ASDs and 15,000 of their family members, we show that polygenic risk for ASDs, schizophrenia, and educational attainment is over transmitted to children with ASDs in two independent samples, but not to their unaffected siblings. These findings hold independent of proband IQ. We find that common polygenic variation contributes additively to ASD risk in cases that carry a very strong acting de novo variant. Lastly, we find evidence that elements of polygenic risk are independent and differ in their relationship with proband phenotype. These results confirm that ASDs' genetic influences are highly additive and suggest that they create risk through at least partially distinct etiologic pathways.

  

The Genetics of Autism: Key Issues, Recent Findings and Clinical Implications

Summary and Conclusions

Autism and related conditions are highly heritable disorders. Consequently, gene discovery promises to help elucidate the underlying pathophysiology of these syndromes and, it is hoped, eventually improve diagnosis, treatment, and prognosis. The genetic architecture of autism is not yet known. What can be said from the studies to date is that writ large, autism is not a monogenic disorder with Mendelian inheritance. In many, but clearly not all individual cases, it is likely to be a complex genetic disorder that results from simultaneous genetic variations in multiple genes. The CDCV hypothesis predicts that the risk alleles in Autism and other complex disorders will be common in the population. However, recent evidence both with regard to autism and other complex disorders, raises significant questions regarding the overall applicability of the theory and the extent of its usefulness in explaining individual genetic liability. In addition, considerable evidence points to the importance of rare alleles for the overall population of affected individuals as well as their role in providing a foothold into the molecular mechanisms of disease. Finally, there is debate regarding the clinical implications of autism genetic research to date. Most institutional guidelines recommend genetic testing or referral only for idiopathic autism if intellectual disability and dysmorphic features are present. However, recent advances suggest that the combination of several routine tests combined with a low threshold for referral is well-justified in cases of idiopathic autism.

So What is Autism? 

Most people’s autism is of unknown cause (idiopathic) and this is most likely to be polygenic, but highly likely to have some environmental influences making it multifactorial.

What is interesting and potentially relevant to therapy is that the polygenic footprint of autism overlaps with those causing other neuropsychiatric diseases like bipolar, schizophrenia and even ADHD.

As you broaden the definition of autism and so move the threshold you will eventually diagnose everyone as having autism; because we all have some autism genes.

Autism genes are in all of us, new research reveals

This does then start to be ridiculous, but in some ways we are now at the point where quirky but normal has become quirky autistic.

This same questionable position of where to draw the threshold applies to all such disorders (bipolar, ADHD etc.).  At what point does a difference become a disorder?

Where things currently stand more than 10% of the population have an autism-gene-overlapping diagnosis.  That is a lot and suggests that things are getting a little out of control.  Perhaps better to raise the threshold for where difference become disorder?

 Percent of the population affected by various disorders genetically overlapping to strictly define autism (SDA). Estimates of prevalence vary widely by country and study.

If you raise the threshold for how severe autism has to be, you soon lose the quirky autism. A stricter approach to diagnosing ADHD would mean losing the people that will naturally “grow out of it” and leave a much smaller group that might genuinely benefit from medical intervention. We saw in an earlier post that the percentage of kids with ADHD given drugs varies massively among developed countries, with the US at the top and France at the bottom. Here is another article on this subject.

Why French Kids Don't Have ADHD

Autism overlapping with Schizophrenia, Bipolar ADHD etc.

There are now numerous different studies showing how the large number of genes that underlie each observational diagnosis overlap with each other.

Shared molecular neuropathology across major psychiatric disorders parallels polygenic overlap

One Sentence Summary: Autism, schizophrenia, and bipolar disorder share global gene expression patterns, characterized by astrocyte activation and disrupted synaptic processes.

Recent large-scale studies have identified multiple genetic risk factors for mental illness and indicate a complex, polygenic, and pleiotropic genetic architecture for neuropsychiatric disease. However, little is known about how genetic variants yield brain dysfunction or pathology. We use transcriptomic profiling as an unbiased, quantitative readout of molecular phenotypes across 5 major psychiatric disorders, including autism (ASD), schizophrenia (SCZ), bipolar disorder (BD), depression (MDD), and alcoholism (AAD), compared with carefully matched controls. We identify a clear pattern of shared and distinct gene-expression perturbations across these conditions, identifying neuronal gene co-expression modules downregulated across ASD, SCZ, and BD, and astrocyte related modules most prominently upregulated in ASD and SCZ. Remarkably, the degree of sharing of transcriptional dysregulation was strongly related to polygenic (SNP-based) overlap across disorders, indicating a significant genetic component. These findings provide a systems-level view of the neurobiological architecture of major neuropsychiatric illness and demonstrate pathways of molecular convergence and specificity.

We observe a gradient of synaptic gene down-regulation, with ASD > SZ > BD. BD and SCZ appear most similar in terms of synaptic dysfunction and astroglial activation and are most differentiated by subtle downregulation in microglial and endothelial modules. ASD shows the most pronounced upregulation of a microglia signature, which is minimal in SCZ or BD. Based on these data, we hypothesize that a more severe synaptic phenotype, as well as the presence of microglial activation, is responsible for the earlier onset of symptoms in ASD, compared with the other disorders, consistent with an emerging understanding of the critical non-inflammatory role for microglia in regulation of synaptic connectivity during neurodevelopment (39, 66). MDD shows neither the synaptic nor astroglial pathology observed in SCZ, BD. In contrast, in MDD, a striking dysregulation of HPA-axis and hormonal signalling not seen in the other disorders is observed. These results provide the first systematic, transcriptomic framework for understanding the pathophysiology of neuropsychiatric disease, placing disorder-related alterations in gene expression in the context of shared and distinct genetic effects.

  

Common polygenic variation contributes to risk of schizophrenia that overlaps with bipolar disorder

Schizophrenia risk genes tied to immunity, autism

Several of the variants lie in regions important for immune function and associated with autism. This suggests that both disorders stem partly from abnormal activation of the immune system, say some researchers.

Brain tissue study bolsters autism, schizophrenia link

The study builds on previous work, in which Arking’s team characterized gene expression in postmortem brain tissue from 32 individuals with autism and 40 controls². In the new analysis, the researchers made use of that dataset as well as one from the Stanley Medical Research Institute that looked at 31 people with schizophrenia, 25 with bipolar disorder and 26 controls³.

They found 106 genes expressed at lower levels in autism and schizophrenia brains than in controls. These genes are involved in the development of neurons, especially the formation of the long projections that carry nerve signals and the development of the junctions, or synapses, between one cell and the next. The results are consistent with those from previous studies indicating a role for genes involved in brain development in both conditions.

“On the one hand, it’s exciting because it tells us that there’s a lot of overlap,” says Jeremy Willsey, assistant professor of psychiatry at the University of California, San Francisco, who was not involved in the work. “On the other hand, these are fairly general things that are overlapping.”

Full paper

Transcriptome analysis of cortical tissue reveals shared sets of downregulated genes in autism and schizophrenia

Schizophrenia/Bipolar linked to Creativity? Autism linked to Intelligence?

Since we see that neuropsychiatric disorders are substantially polygenic, the question arises why they have been evolutionarily conserved. Over thousands of years why have these traits not just faded away?

That question was raised, and answered again, in a recent autism study at Yale.  The same wide cluster of genes that may lead trigger autism are again seen to be linked to higher intelligence. You may get autism, higher intelligence, both or indeed neither, but people with those genes have a higher likelihood of autism and/or a higher IQ.

Previous studies have linked bipolar/schizophrenia to creativity, so you would expect artists and stage actors to have a higher incidence of those disorders.

In terms of evolutionary selection, clearly creativity and intelligence have been valued and so the associated disorders did not fade away over thousands of years.
  

Genetic risk of autism spectrum disorder linked to evolutionary brain benefit

“It might be difficult to imagine why the large number of gene variants that together give rise to traits like ASD are retained in human populations — why aren’t they just eliminated by evolution?” said Joel Gelernter, the Foundations Fund Professor of Psychiatry, professor of genetics and of neuroscience, and co-author. “The idea is that during evolution these variants that have positive effects on cognitive function were selected, but at a cost — in this case an increased risk of autism spectrum disorders.” 

Schizophrenia, bipolar disorder may share genetic roots with creativity

Common polygenic risk for autism spectrum disorder (ASD) is associated with cognitive ability in the general population.

Abstract

Cognitive impairment is common among individuals diagnosed with autism spectrum disorder (ASD) and attention-deficit hyperactivity disorder (ADHD). It has been suggested that some aspects of intelligence are preserved or even superior in people with ASD compared with controls, but consistent evidence is lacking. Few studies have examined the genetic overlap between cognitive ability and ASD/ADHD. The aim of this study was to examine the polygenic overlap between ASD/ADHD and cognitive ability in individuals from the general population. Polygenic risk for ADHD and ASD was calculated from genome-wide association studies of ASD and ADHD conducted by the Psychiatric Genetics Consortium. Risk scores were created in three independent cohorts: Generation Scotland Scottish Family Health Study (GS:SFHS) (n=9863), the Lothian Birth Cohorts 1936 and 1921 (n=1522), and the Brisbane Adolescent Twin Sample (BATS) (n=921). We report that polygenic risk for ASD is positively correlated with general cognitive ability (beta=0.07, P=6 × 10(-7), r(2)=0.003), logical memory and verbal intelligence in GS:SFHS. This was replicated in BATS as a positive association with full-scale intelligent quotient (IQ) (beta=0.07, P=0.03, r(2)=0.005). We did not find consistent evidence that polygenic risk for ADHD was associated with cognitive function; however, a negative correlation with IQ at age 11 years (beta=-0.08, Z=-3.3, P=0.001) was observed in the Lothian Birth Cohorts. These findings are in individuals from the general population, suggesting that the relationship between genetic risk for ASD and intelligence is partly independent of clinical state. These data suggest that common genetic variation relevant for ASD influences general cognitive ability.

  

Conclusion

Given the overlap between so many neuropsychiatric disorders it might be helpful if psychiatrists were more aware of the limitations of their observational diagnoses.

There is no singular schizophrenia like there is no single autism. They are all intertwined.  A mood disturbance in Asperger’s may have plenty in common with one in schizophrenia and respond to the same therapy.  Not surprisingly an off-label treatment in autism may work wonders for someone who is bipolar.

Probably the tighter you define autism the more there will be biological overlaps with bipolar/schizophrenia.

While there are overlaps there are other areas where autism is the opposite of bipolar and/or schizophrenia.

From a therapeutic perspective, since schizophrenia therapies have been more deeply researched than those of autism, it is always well work checking schizophrenia research for evidence.

The multifactorial approach does help explain the increasing incidence of more severe autism as environmental insults increase in modern life and we accumulate epigenetic damage.  The studies linked autism/schizophrenia with immunity genes and there is has been a continuing rise in other auto-immune, disease like asthma.

The ever sliding diagnosis threshold substantially explains much of the great increase in mild autism.

You can also use this framework to work out how to reduce the incidence of autism in future generations, but it seems that human nature continues to work in the opposite way.

Partner preferences may contribute to autism prevalence

Environmental factors are simple to modify, reducing risk factors and increasing protective factors.

If you think like Knut Wittkowski you might look at the tail of autism liability curve and try to identify those future people. Those people are likely to have some of the 700 autism risk genes over/under expressed and might benefit from some preventative therapy to minimize the coming developmental damage.  Knut thinks that Mefanemic acid will do the job. There are numerous other ideas.