For the first time, molecular-level changes have been detected in the brains of depressed women. The findings reveal that there is a connecting link between the two hypotheses of biological mechanisms leading to mental illness. The research was conducted by scientists at School of Medicine, University of Pittsburg and findings were published in the journal Molecular Psychiatry.

The study author Dr. Etienne Sibille, Associate Professor, Pitt School of Medicine, noted that very  little research has been done on mental illnesses of women, although they are twice as likely as men to suffer from severe and frequent depression. The outcomes of research will provide better understanding of one of the most common psychiatric illnesses.

In the study, post-mortem brain tissue samples of 21 depressed women and 21 similar women without any history of depression were examined. The researchers observed reduced expression of certain genes, including the one for brain-derived neurotrophic factor (BDNF), in depressed women as compared to their peers. Also, the expression of genes responsible for neurotransmitter gamma-aminobutyric acid (GABA) was drastically low in depressed women. These changes were observed in amygdala, a part of human brain responsible in sensing and expressing emotion.

The scientists next focused on the impacts of BDNF on GABA cells by genetically engineering mice to carry different mutations in BDNF gene. They identified two mutations that led to same reduction in GABA subtype and also reflected other changes witnessed in depressed human brains. The finding will enhance future research on depression.

Psychiatrists and researchers have surmised many times in the past that reduced BDNF levels play key role in depression, and they have also hypothesized that reduced activity of GABA is an important factor.

Dr. Sibille said that their work has linked the two concepts together by demonstrating that, first, BDNF is evidently low in depression and, second, low BDNF influences particular subtypes of GABA in a way that develops characteristics we observe in depressed brains.

The researchers have continued with exploration of molecular pathways between BDNF and GABA. The project received funding from National Institute of Mental Health.