Patients have always been told that it takes antidepressants 4-6 weeks before they notice any improvement in their depression. However, a new study claims that a single dose will place significant changes in the brain within hours.

Approximately 1 in 10 adults report some form of depression and 1 in 10 people with depression over the age of 12 take antidepressants for the condition.

Brand name drugs which are selective serotonin reuptake inhibitors (SSRIs) include Prozac, Zoloft, and Lexapro. They are believed to boost production of the neurotransmitter serotonin which plays an important role in mood balance.

The research team published their findings in the journal Current Biology. For the study, they investigated how SSRIs worked in the brain chemistry of 22 healthy participants.

The Study

Each participant underwent a 15 minute brain scan to measure the oxygenation of blood flow in the brain. After being given a single dose of an SSRI, Lexapro in this case, they underwent another brain scan just hours later.

The team then compared 3D images of brain scans before and after SSRI usage. They found that the SSRI reduced intrinsic connectivity levels of the brain within 3 hours of taking the SSRI. However, the SSRI increased connectivity in two brain regions, the cerebellum and the thalamus. The cerebellum is involved with voluntary movement while the thalamus is involved in sensory perception and motor function.

They  noted that they were not expecting the SSRI to have an eminent effect due to the short timescale but the study shows that SSRI do alter brain connectivity within hours after the first dosage. The explanation this is that the SSRIs are reorganizing the brain in order to reduce depressive symptoms later.

These findings can help psychiatrist understand which patients with depression respond to SSRIs and which do not.

The team hopes that their work will guide better treatment decisions for those suffering from depression. They plan to move toward clinical trials and would like to compare the brain connectivity of depression patients who have responded to treatment with those who have not.