Numerous studies report that depression is the most common psychiatric disorder of the elderly. According to the behavioral view, depression results from inadequate, ineffective or insufficient positive reinforcement. In contrast, the cognitive position sees depression as a result of negative thinking about oneself, one's experience, and the future. Both behavioral therapy and cognitive therapy can successfully be used as effective therapeutic tools with depressed elderly persons. However, it is unlikely that either of these treatments is adequate or sufficient to treat all depressions of old age. Great variability is a consistent finding in research on the aging, which makes it necessary to remain flexible in determining the problem and selecting an intervention appropriate for the client. Additionally, it is necessary that the therapist feel that older persons can learn new behaviors and cognitions, and that they can respond to the same therapeutic principles as younger persons. (Author)