I see many people in my practice who have taken anti-depressants for long periods of time, sometimes starting in adolescence and continuing for much of their adult life. Many of these people have never had a psychiatric assessment. It is sometimes difficult to determine why anti-depressants were started in the first place because details of memory have become vague or records are hard to get, but in many cases it can be established that the person has never had an episode of severe (melancholic) depression.
There are no objective tests for conditions like anxiety and depression. Diagnosis in psychiatry is based solely on clusters of symptoms. During the 1980s, the definitions of depression were expanded to include less severe forms and, as a result, rates of anti-depressant use sky-rocketed to roughly 10% of the adult population. This resulted in an apparent decline in effectiveness of anti-depressants because the majority of users have less severe (ie. non-melancholic) types of depression in which anti-depressants are often not particularly effective.
But anti-depressants such as SSRIs are not simply placebos with side effects. They affect arousal in the brain in a general way and have been tried in virtually all psychiatric disorders. As with any drug, tolerance occurs with anti-depressants because the body produces counteracting effects. With anti-depressants, the counteracting effects can be easily confused with a worsening of the original problem. This may explain why many people may stay on anti-depressants for years without substantial improvement.
Part of the reason for the high rates of use of anti-depressants has been the way these drugs have been marketed. Some psychiatrists have tried to distance themselves from the ‘chemical imbalance’ theory by saying it was always just a myth or an urban legend. Drug companies were able to turn profits on these drugs despite huge fines imposed for false claims, but some of the larger companies have implicitly acknowledged the poor science behind these drugs by stopping further research in this area.
N.B. Severe depression almost always requires treatment with an anti-depressant, but mild to moderate depression can be treated with psychotherapy and lifestyle changes such as exercise and decreased use of drugs and alcohol. The average length of an untreated episode of depression is 6 months. Anti-depressants usually take 2-4 weeks to start working. If there is no improvement after 6-8 weeks, switching to a drug in a different class of anti-depressants may be helpful. Continue taking anti-depressants after you start to feel better but, in most cases, a plan should be in place for coming off after 6-12 months. When coming off anti-depressants, taper down over 2-3 months to avoid withdrawal symptoms.