For instance, a person's energy level or sleeping or eating patterns may improve before his depressed mood lifts. If there is little or no change in symptoms after 5 to 6 weeks, a different medication may be tried. Some people will respond better to one than another. Since there is no certain way of determining beforehand which medication will be effective, the doctor may have to prescribe first one, then another, until an effective one is found. Treatment is continued for a minimum of several months and may last up to a year or more.
Some people find that their depressions become more frequent and severe as they get older.
Those that are commonly used have no known long-term side effects and may be continued indefinitely. The prescribed dosage of the medication may be lowered if side effects become troublesome. Lithium can also be used for maintenance treatment of repeated depressions whether or not there is evidence of a manic or manic-like episode in the past. Dosage of antidepressants varies, depending on the type of drug, the person's body chemistry, age, and, sometimes, body weight. Dosages are generally started low and raised gradually over time until the desired effect is reached without the appearance of troublesome side effects.