There is increasing interest in understanding the mechanisms by which effective therapies work. The cognitive neuroscience perspective presented here adds to our mechanism understanding of how empirically supported treatments for anxiety and depression work and it informs the cognitive specificity hypothesis. Basic neuroscience findings regarding synaptic transmission and experience-dependent plasticity are presented because they form the basis of learning and memory and enable a better understanding of the effects of neuroleptic drugs on the limbic system. Principles of connectionist modeling are discussed because they provide additional mechanism information. A generalization of the S-O-R model into a network model is presented. A connectionist explanation of how networks transform perceptions into cognitions is provided. This information is used to better understand how placebos and nocebos work. Clinical applications are made to PTSD, anxiety, depression, and their empirically supported treatments. The cognitive specificity hypothesis is revisited from this connectionist cognitive neuroscience perspective. Mechanism information concerning the effects of drugs on cognition, depth of cognitive change, and durability of treatment effects is presented. Corollaries and conclusions follow.