SSRI&#x27;s in my opinion are not the future of antidepressants.  They work by indiscriminately increasing serotonin levels in the synapse, thereby activating every single serotonin receptor (5-HT).  While you get the anti-depressant effect by increasing the activation at the 5-HT1 receptor, you also get the negative side effects of SSRI&#x27;s since it activates 5-HT2c receptor (weight gain), 5-HT3 receptor (nausea), and sleep issues.<p>The future of the antidepressants lies in chemicals that increase serotonin at the 5-HT1 receptor (lowering depression) without affecting the other receptors.  Drugs like mirtazipine and nefazodone attempt to do this by blocking certain 5-HT receptors (mainly the 5-HT2a receptor, which lowers anxiety), and as a result make serotonin levels higher and more available at the 5-HT1 receptor.  That&#x27;s the reason these 2 drugs in particular don&#x27;t have the nasty side-effects of SSRI&#x27;s.<p>The future of anti-depressants likely lies in the ability to find a drug that increases activation at the 5-HT1 receptors in certain parts of the brain, while leaving the rest of the brain and receptors untouched.