They were named SSRIs because they affect the serotonin-containing nerves in the brain. SSRIs are often preferred to other antidepressants because they are safe, easy to use and their side-effects are usually less severe than the tricyclics. They are less toxic in overdose than TCAs, and do not require laboratory testing of blood levels. This is another 'class' of drug with only one member, venlafaxine. Venlafaxine is similar in tolerability and safety to the SSRI's.
Trazodone appears similar, but with little effect on noradrenaline.
Buspirone is also atypical and is used for the treatment of anxiety with or without depression. There is evidence that used with other medications, it may help people who do not benefit from antidepressants alone. Other drug treatments and ECT Mood stabilisers Lithium and the anticonvulsant drug carbamazepine are sometimes given for severe depression where antidepressants have failed to help. See Treatment of bipolar disorder . They have a range of side-effects and people taking them need to be monitored closely.