
What Caused This to Happen?
This is usually one of the first questions asked by patients and their families following a psychotic episode, suicide attempt, or manifestation of any serious mental illness. More from the Director of NIMH.
“What caused this to happen?” is usually one of the first questions asked by patients and their families following a psychotic episode, suicide attempt, or manifestation of any serious mental illness. In earlier times, the explanations ranged from an imbalance of the “humours” to demonic possession. More recently, there have been “schizophrenogenic” or “refrigerator” mothers and “abusive” or “toxic” fathers. Modern scientists and clinicians point to a mix of genetic and environmental factors but these explanations are rarely satisfying and do little to stem the tide of guilt, shame, and blame that surrounds mental illness as much today as during the witch hunts of centuries past.
Of course, genetics and environment are important. But their effects are probabilistic. With the exception of a few rare mutations that appear causal for autism, genetics confers a tendency for height, personality, and risk for mental illness through the aggregate effects of hundreds of common variations in the genome. This information may be useful in populations, but it is of little help in explaining cause for any individual.
[[{"type":"media","view_mode":"media_crop","fid":"31025","attributes":{"alt":"severe mental illness","class":"media-image","id":"media_crop_1997330928874","media_crop_h":"0","media_crop_image_style":"-1","media_crop_instance":"3277","media_crop_rotate":"0","media_crop_scale_h":"0","media_crop_scale_w":"0","media_crop_w":"0","media_crop_x":"0","media_crop_y":"0","title":" ","typeof":"foaf:Image"}}]]Environment or, more accurately, experience is undeniably a factor for PTSD, but for most other forms of mental illness the link is difficult to prove. We use terms like “adversity,” “toxic stress,” or “trauma,” recognizing that our assays of these experiences are woefully imprecise and knowing that subjective experience, especially memories of childhood experience, may trump any objective measure of the event. None of these factors have prevented patients and clinicians from assuming that “trauma” is the cause of most mental illness, perpetuating a culture of blame that has permeated mental health care for a century.
The scientific answer to the question of “what caused this to happen?” is to cite a mixture of genetic and environmental factors, often expressed as a gene-environment interaction. The honest answer to the question of cause is that we don’t know. Gene-environment interaction is a multi-syllabic way of saying “we don’t know.” Our minds seek explanations to reduce the mystery and pain of mental illness, but in truth, we are early in our search for understanding how, when, and where these disorders develop.
I found myself thinking about all of this after reading a recent paper on cancer. In last week’s Science,
What is stunning about the paper by
These results suggest that only a third of the variation in cancer risk among tissues is attributable to environmental factors or inherited predispositions. The majority is due to “bad luck,” that is, random mutations arising during DNA replication in normal, noncancerous stem cells. This is important not only for understanding the disease but also for designing strategies to limit the mortality it causes.
There are exceptions-lung cancer and smoking, skin cancer and sun exposure-but for most forms of cancer, the data suggest the “cause” is “bad luck.”
What does this have to do with mental illness? Outside of a few areas of the brain, adult neurons don’t divide and exuberant cell replication is unlikely to be the cause of schizophrenia or depression. The link starts much earlier. In fact, between weeks 4 and 24 of gestation, the human brain is generating 100,000 cell divisions every minute-arguably a
President Lincoln’s famous line that “a tendency to melancholy is a misfortune not a fault” comes to mind. We need explanations. “Bad luck” is not particularly satisfying as an explanation of cause, but that does not make it wrong. Of course, genetics and environment influence brain development during gestation. And we don’t know that this new explanation, which seems so attractive for cancer etiology, has any relevance at all to autism or schizophrenia. But this new report for cancer serves as a useful reminder that we really know too little about “what caused this to happen” when someone we care about develops a mental illness. And the real cause may be something that is, unfortunately, out of our control.
Dr Insel is Director of the National Institute of Mental Health (NIMH).
Note: This article,
References:
1 Tomasetti C, Vogelstein B. Cancer etiology. Variation in cancer risk among tissues can be explained by the number of stem cell divisions. Science. 2015;347:78-81.
2 Insel TR. Brain somatic mutations: the dark matter of psychiatric genetics? Mol Psychiatry. 2014;19:156-158.
Newsletter
Receive trusted psychiatric news, expert analysis, and clinical insights — subscribe today to support your practice and your patients.