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These days, it is increasingly recognized that mental health problems can be just as debilitating as physical ones. Unfortunately, much of what we thought we knew about the causes of mental illness has recently been proven to be wrong.
In some ways, this is not surprising, says Allen Francis of Duke University in North Carolina, lead author of a major US psychiatric textbook. Diagnostic and Statistical Manual of Mental Disorders IV. “The brain is the most complex in the known universe, and its secrets are revealed very slowly,” he says.
A few decades ago, it seemed like we were trying to unlock the secrets of some mental health conditions. Abnormal levels of various brain chemicals are thought to be the cause, and may be ameliorated with medication. For example, depression was thought to be caused by a deficiency of the brain signaling messenger serotonin, with the most common class of antidepressants also increasing levels of serotonin. Genetic studies have also found that people with depression are more likely to carry gene mutations that lower serotonin. Schizophrenia was thought to be caused by excessive activity in circuits involving another brain chemical called dopamine.
However, this amazing photo turned out to be a mirage. Emerging evidence suggests that low serotonin is not the cause of depression, and many of the early genetic studies that suggested a single brain chemical was responsible for certain symptoms are now outdone. It was conducted using scientific methods that are believed to be flawed.
Mental health conditions have a strong genetic component. For example, people with identical twins who have schizophrenia have about an 80% chance of developing schizophrenia.
