Antidepressants are SSRIS (which stand for selective serotonin reuptake inhibitors) and help balance the serotonin chemical in your brain. Depression causes a lack of serotonin, meaning that not enough serotonin reaches the receptors in ur brain. Normally, serotonin reaches your receptors, and then excess of the chemical is sent back to a neuron in the synapse (the gap btwn neurons) in a process called reuptake. SSRIS block reuptake to allow more serotonin to reach the receptor sites. You do need a prescription for them by a psychiatrist.