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Mood disorders

Genes, The Environment And Mood

Mood disorders such as depression, anxiety, and bipolar disorder are relatively common—affecting one in five people—and can be debilitating. Depression involves feelings of sadness, low energy, and often sleep disruptions. Bipolar disorder involves depression with periods of mania, a condition that consists of an overabundance of energy and a conviction that one is on the verge of doing great things. Mania can involve spending sprees, expensive travel, and very grandiose ideas.


These disorders are unique because their effects can be temporary and changeable—people with depression or anxiety aren’t usually permanently depressed or anxious, and people with bipolar disorder swing between the two extremes. This instability makes finding genes for these disorders challenging, though we know the essential role genetics plays. Genes cause a predisposition for the conditions, genes determine one’s likelihood of recovery, and something in the environment triggers how these genes are expressed in the brain.

About 2.8% of U.S. adults have bipolar disorder

40% of Americans experience depression at some point in their lifetime
Nearly 83% of bipolar disorder cases are classified as severe

Lieber is examining the intersection of genes and the environment in the development of mood disorders. Identifying the underlying genes and the environmental triggers that turn them on during development could allow doctors to evaluate risk and even prevent or cure these conditions. Lieber researchers, for example, have identified the first conclusive link between air pollution and depression. The more air pollution a person is exposed to, the more depression they are at risk of experiencing. The research could inform policy to reduce pollution and help people at high risk of mood disorders to seek lower pollution places to live.

“Understanding what and how environmental risks act on genes in affecting brain function at the core of psychiatric disability could help us define new and improved treatment strategies, ranging from public health policies to personalized medicine.”

Hao Yang Tan, MD, Lead Investigator