Each class effectively treats Depression but since they act on different neurotransmitters, each has different side effects. These are the oldest and most common antidepressants but they can have numerous side effects such as blurred vision, dry mouth, weight gain, and constipation. However, eating foods containing high amounts of tryamine or taking medicines containing noradrenaline can cause a severe adverse reaction known as hypertensive crisis. Therefore,when taking medicine in this class, it is extremely important that the physician provides a list of foods and medicines to avoid. However, there is a relatively new MAOI medicine called Moclobemide that has a minimal effect on the enzyme in the stomach and does not require the same diet and medication restrictions.
Some antidepressants affect many neurotransmitters together with noradrenaline and serotonin.
But medicines in this new group, SSRI's, were designed specifically to affect only serotonin. This eliminates a lot of side effects associated with older and more established antidepressants. But SSRI's can cause insomnia, so they are usually taken in the morning. These drugs are less dangerous if taken in overdose, thereby reducing the risk of suicide. The possible side effects are insomnia, agitation, or weight loss .