Twin studies reliably report a nearly 50% heritability rate for depression. Dr. Shock MD PhD’s recent post speculates why:
- There are different subtypes of depression such as melancholic type, Seasonal Affective Disorder, Bipolar depression. These different types of depression will not be explained by one gene or set of genes, or polymorphisms of genes.
- Research until now may have varied in inclusion criteria and diagnostic criteria
- Genes responsible for depression may differ with ethnicity. Chines might have different gene locations responsible for depression than Caucasian depressed patients
- Besides ethnicity, gender may also play a role in genetics, depression is twice as common in females than males.
- Depression is a complicated disease. Different systems could affected. A variety of different neurotransmitters and hormones can be involved. In some patients the cortisol stress system is involved with depression in others not. In some patients SSRIs are effective, others need other kind of antidepressants or treatments.
- And last but not least, depression can have many causes of which heritability is just one and it doesn’t have to be present at all.
All this talk about SSRIs, placebos, and the like accentuates just how little we know about depression. Our current diagnostic, therapeutic, and research agendas seem to have missed something. We’re lost in the meshwork of mental processes – swimming in a sea of ever-ebbing tides and unexpected undertows.
I often express a frustration with the poor selectivity of psychotropic medications. They are, at times, akin to carpet bombing the brain, opting to (in the case of anxiolytics) sedate all neural activity over a lack of treatment. However, when contextualized by our lack of understanding due to the brain’s complexity, the transient nature of mental states, and our knowledge deficit carpet bombing becomes strategically appropriate. It’s the best we have to offer.
Our best isn’t good enough. The mental health field has a lot to improve upon. We need to do research about which therapies are effective for which disorders. We need more selective medications. We need to methodically sort out the diagnostic and therapeutic differences between types of disorders. And we certainly need to publish the fifth edition of the aging DSM; we must know what we’re treating before we can treat it.