Behavioral activation
Behavioral Activation is a third generation behavior therapy. It is one of many functional analytic psychotherapies which are based on a Skinnerian psychological model of behavior change, generally referred to as Applied Behavior Analysis. This area is also a part of what is called Clinical Behavior Analysis (CBA) and makes up one of the most effective practices in the professional practice of behavior analysis.

# Theoretical underpinnings
Behavioral activation emerged from a component analysis of cognitive behavioral therapy. This analysis found that the cognitive component added little to the overall treatment  The behavioral component had existed as a stand alone treatment in the early work of Lewisohn and thus a group of behaviorists decided that it might be more efficient to pursue a purer behavioral treatment for the disorder. The theory holds that not enough environmental reinforcement or too much environmental punishment can contribute to depression. The goal of the intervention is to increase environmental reinforcement and reduce punishment.
The theoretical underpinnings of behavioral activation for depression is Fersters (1973) functional analysis of depression. Ferster's basic model has been strengthened by further development in the study of reinforcement principles which led to the matching law and continuing theoretical advances in the possible functions of depression , as well as a look at behavior analysis of child development; to determine long term patterns which may lead to dystimia.

# Methods
A Behavioral Activation (BA) approach to depression was as follows. Participants were asked to create a hierarchy of reinforcing activities which were then rank-ordered by difficulty. Participants tracked their own goals along with clinicians who used a  to reinforce success in moving through the hierarchy of activities. Participants were measured before and after using a Beck Depression Inventory (BDI) and were found to have a large effect on their depression as a result of their treatment. This was then compared to a control group who did not receive the same treatment. The results indicate that those who received Behavioral Activation treatment was markedly superior than to those in the control group. Multiple clinics have since piloted  and developed the treatment 

# Research support
A recent review of behavioral activation studies for depression find that it as a robust effect and that policy makers should consider it an effective treatment. A large scale treatment study found behavioral activation to be more effective then cognitive therapy and on par with medication for treating depression. .
Recently, behavioral activation has been applied to anxiety and appears to have promising results . One study in particular found it to be effective with Fibromyalgia-related pain anxiety .

# Future Direction
Several proponents of behavior therapy believe that behavioral activation will have much to offer other areas such as post traumatic stress disorder .

# Other Third Generation Behavior Therapies
Other Behavior Therapies are Acceptance and Commitment Therapy (ACT), as well as Dialectical Behavior Therapy (DBT) and Functional Analytic Psychotherapy (FAP). Behavioral Activation owes its basis to Charles Ferster's Functional Analysis of Depression (1973) which developed B.F.Skinner's analysis of depression as a lack of reinforcement; consistent with his analysis of motivation.