Even if they’re effective, antidepressants with less side effects have mostly displaced them in clinical practice. Cyclic antidepressants, on the other hand, may be a suitable choice for certain patients. When other therapies have failed, they may provide relief from depression in certain situations.
Antidepressants are used for a variety of reasons, obviously as antidepressants, but also may be used for:
It is theorized that depression results from a deficiency of norepinephrine, dopamine or serotonin. These are biogenic amines, norepinephrine and serotonin are released throughout the brain by neurons that react with multiple receptors to regulate arousal or waking up alertness, attention, moods, appetite and sensory processing.
Deficiencies may occur from three known reasons.  Mono amine oxidase may break them down to be recycled or they are restored in the neuron.  Rapid Fire of the neurons may lead to their depletion.  The number or sensitivity of the postsynaptic receptors may increase depleting neurotransmitter levels.
The use of drugs that alter the concentration of neurotransmitters in the brain is the most effective means of treating depression.