In psychiatry, drugs used to treat mental illnesses also perform such manipulations. For depression, millions of people take drugs like Prozac and Zoloft that inhibit the reuptake of the neurotransmitter serotonin. How these drugs alleviate depression may involve the production of new neurons in the hippocampus as well as increased availability of serotonin in the synaptic gaps between existing neurons. Other antidepressants, such as MAO inhibitors, affect neurotransmitters in different ways. Bipolar disorder, formerly known as manic depression, can be effectively treated with lithium, which affects various neurotransmitters. The often devastating disease schizophrenia can sometimes be treated with drugs like Thorazine and Risperdal that inhibit dopamine and also can affect levels of other neurotransmitters. Increasing concentrations of dopamine can alleviate the symptoms of Parkinson's disease.