Major Depressive Disorder (MDD)

MDD is a highly prevalent disorder that afflicts 20% of the population in their lifetimes, and ranks high in morbidity among all human diseases. It is more prevalent in women than men (roughly 2:1 ratio), and presents differently in different people (in terms of symptoms, onset, recurrence and comorbidity). Its biological nature remains unknown, despite advances in modern medicine, and its diagnoses and treatments remain empirical. On the one hand, misdiagnosis and overprescription of antidepressants are both commonplace; on the other, 50% of individuals with the disorder never make it into a clinic to get diagnosed, and 50% of diagnosed cases do not respond to their first prescribed medication. It is needless to say that we need to do better here. 

The state of understanding of MDD now is rather like that of cancer 100 years ago. Back then, without an understanding of the genome's structure and its pathogenic nature (i.e. mutations leading to disregulated cellular proliferation), cancer was a mystery too. In particular, no one knew that leukemias and solid tumours were, in fact, of a similar nature. Fast forward 100 years, we now know something of nature of cancer, though it remains a difficult problem to solve. MDD, and psychiatric disorders in general, however, have not reached this state. 

What is the nature of MDD? Is it some specific neurons not firing right in a massive way, or all neurons not firing right in a sutble way, or has it nothing to do with neurons firing? How would we ever know? These are the questions our research tries to answer, using quantitative genetics as a tool.