There is no scientific evidence that any mental disorder-- including depression-- is caused by serotonin abnormalities. Dangerously high serotonin levels resulting in serious illness and even death, however, are often caused by serotonin drugs like SSRIs and SNRIs-- especially when a patient is prescribed two or more of these drugs simultaneously.
Dr. Wayne Goodman, Chairman of Psychopharmacologic Committee of the FDA said, "Biological psychiatrists have looked very closely for a serotonin imbalance or dysfunction in patients with depression or OCD, and to date it has been elusive. [They found no link] Although an SSRI or antidepressant may work well in an individual, this doesn't prove there's an underlying imbalance, defect, or dysfunction in the person's serotonin system."
The four current guesses why antidepressants may work are the following:
1. Changes in neurotransmitters.
2. Placebo effect.
3. Neurogenesis (new brain cell growth).
4. Amphetamine-like side-effects give the patient more energy.
How do antidepressants work? Nobody knows.
Antidepressants physically alter the brain. Once drugs are withdrawn, does the brain fully restore? Nobody knows.
What are the long-term effects of antidepressants? Nobody knows.