In addition to acting on GABA receptors and neurotransmitters, alcohol can affect the brain’s levels of serotonin and dopamine—both of which play a role in mood and mental function. Imbalances in these neurotransmitters can increase the risk for mental illnesses such as depression, generalized anxiety disorder, borderline personality disorder, and schizophrenia. In fact, co-occurring mental health disorders are present in approximately 50% of people who are diagnosed with substance use disorders.