If you understand the pharmochologics of antidepressants and the neurotransmitter action in the brain, you cannot question that antidepressants must have a significant effect upon depression. It involves the transmission of messages from one neuron to another neuron and the neurotransmitters that assist in that transmission. Antidepressants as well as other psychotropic medications have any number of actions upon these chemicals that enhance the communication capabilities of these neurons and alter whether or not a person develops or continues to suffer several mental illnesses. I cannot think of a single antidepressant that can be accused of contributing to a "placebo" affect. I've taken antidepressants since they were first developed up until the present day. My first prescription was written in 1978.