If one could select one book that would give the most useful information about understanding mental illnesses from a scientific standpoint, I think it would have to be this book.  Written by prominent psychiatric genetic researchers, it summarizes three decades worth of work by Kenneth Kendler and his collaborators.

Around 1980, when Kendler started his work in this field, psychiatric genetics was not an extremely popular field; psychoanalytic theories still enthralled, and, to the extent that any work had been done in genetics, it had been done in schizophrenia.  Kendler’s life work has been to seriously study depression and anxiety from a psychiatric genetic perspective.  In the process, his research has touched on many related conditions — substance abuse, personality disorder, and even cultural topics, such as the genetics of social and political and religious attitudes.  By taking the powerful methodology of genetic research, and applying it to the most common clinical presentations in psychiatry — depression and anxiety and related topics — Kendler’s work has been immensely important.

I had the benefit of knowing and working with Kendler’s group in the late 1980s, when I was a medical student, and I can attest to the inspirational ambience of the group: research was an exciting adventure of seeking new knowledge and of thinking new thoughts, without any fear about what that knowledge might be.  This attitude has proven quite successful, with hundreds, if not thousands, of scientific papers produced in the last three decades. I’ve tried to keep up with these complex and frequent publications. It is a difficult task.

But it is made moot by this book, which brings together the essence of all that research in one place. I will leave it to readers to see it for themselves, but here I will just highlight a few of the typical findings:

1. The heritability of major depression is only 37%, which is similar to personality traits.  This reflects important genetic aspects to depression, but it highlights just as important, if not more important, environmental components.  (p. 374)
2. The environmental component is specific to each twin, not shared between them, and thus NOT reflective of family or culture — contrary to the assumptions of many theorists of our day, especially of the postmodernist school. Our intellectual leaders have yet to acknowledge, much less grapple with, this fact.
3. Heavy caffeine use has a 77% genetic predisposition (p. 96)
4. Parental death seems to specifically increase the risk, in children, of later adult depression; parental divorce is nonspecific in its later effects on anxiety or depressive or other conditions (pp 138-140)
5. The types of specific adult life events that predispose to triggering a depressive episode tend to involve loss or humiliation (pp 158-160)
6. Social support has very little benefit in protection against depression (pp 162-164).
7. In depression, the genetic risk is constant over time, from childhood to adulthood; environmental risks tend to be recent and have short-lived effects. (pp. 185-186
8. Contrary to popular assumptions, regarding risk of depression, genetic effects are greater in adulthood than childhood, and environmental effects are greater in adulthood than childhood (p. 191).

Using science and not mere opinion, if you want to understand depression and anxiety — and, since those conditions are at the heart of the most common psychiatric presentations — if you want to understand psychiatry, read this book.

© 2011 Nassir Ghaemi

Nassir Ghaemi, MD MPH, Professor of Psychiatry and Pharmacology; Director, Mood Disorders Program, Tufts Medical Center