Is Depression Hereditary?

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Depression is one of the most common and serious illnesses in the world, but sadly also the most mysterious. Experts still do not know what causes the illness, how to diagnose it physically, or treat it effectively. However, we can garner important information by studying depression in families.

First of all, we know that depression runs in families, which implies the influence of particular genes that may render an individual vulnerable to the illness. However, genes are just part of the picture. A child not only inherits genes; he or she inherits a family. Very often, families with mental or behavioral disorders are also families in which there exists a considerable amount of dysfunction. That implies the influence of environment as well as genes.

Indeed, population studies reveal that depression is more likely to occur in homes where abuse and conflict are persistent. Further research has shown that individuals who come from an environment rife with emotional conflict suffer more severe forms of depression and are less likely to respond to existing medications or treatments.

So the next question is: How does this occur? How is it that the experience of the family might become embedded, literally, in the biology of an individual and render them more vulnerable to depression?

What recent research tells us is that — in humans as well as laboratory mice — neglectful or abusive interactions between the parents and the offspring can render the offspring more reactive to the stressors in their environment. Meanwhile, studies in humans show that individuals who are more reactive to stressors in the environment are in turn more likely to develop depression.

What is the mechanism by which the environment can render an individual more reactive to stress and more vulnerable to depression? This question is at the root of the field of epigenetics: the study of how external or environmental factors can switch genes on and off without actually changing the structure of the genes in a given DNA sequence.

My laboratory is dedicated to understanding the epigenetics of depression. We are studying the brain regions that are developmentally influenced by family life, and we are starting to unravel how it is that stress-induced changes in activity in those brain regions leads to depression.

This work can reveal why some individuals faced with severe stress remain resilient and why others develop major depressive illness. Our work is providing clues that there is a true independent biology of resilience that can lead us to incredible new discoveries in understanding ways to treat depression.

Michael J. Meaney, Ph.D., the James McGill Professor in the Departments of Psychiatry, Neurology, Neurosurgery at McGill University, is a researcher with the Hope for Depression Research Foundation.