How Do Drugs From 1 Psychiatric Disorder Treat Symptoms of Another
How is it that Lamotrigine, an antiepileptic, can help depression, a seemingly different disorder altogether? And why can Prozac, an antidepressant, help reduce anxiety? Or an antipsychotic for schizophrenia help depression? In other words, how is it that drugs for one type of major psychiatric disorder treat the symptoms of another type?
The root causes of psychiatric illnesses such as bipolar disorder, major depression, schizophrenia, autism and ADHD are far from understood. Even so for more than 125 years, clinicians have based diagnosis on groups of symptoms observed in patients. Many psychiatrists have thought for a long time now that the current categories don’t really make sense, and that new categories should be based not on symptoms but on the underlying biology.
Moving in that direction more than 300 scientists at 80 research centers in 20 countries scientists have now found that the five psychiatric disorders mentioned above share a common genetic basis. The overlap of these disorders was highest between schizophrenia and bipolar; moderate for bipolar and depression and for ADHD and depression; and low between schizophrenia and autism.
These findings still leave much of the inherited genetic contribution to the disorders unexplained. And none of this accounts for the non-inherited genetic factors that go into determining what a person is like. However, they demonstrate that science is now moving toward understanding the molecular basis of psychiatric illness, which could provide insight into the biological pathways that may predispose someone to health or disease. All this could ultimately lead to new treatments.
Genetic inheritance does not mean our fate is carved in stone, i.e. that because we are wired in a particular way genetically our fate is sealed. This is because it has become increasingly clear over the last 10 years or so that environmental factors determine which of our genes are “turned on” and which are “turned off”. In the scientific literature this is often spoken of as which genes are “expressed” and which are not. Whether your genes are turned on or turned off matters just as much as much as which genes you have.