A psychomotor stimulant theory of addiction.

The theory is advanced that the common denominator fa wide range of addictive substances i their ability to cause psychomotor activation. This view is related to the theory that all positive reinforcers activate acommon biological mechanism associated with approach behaviors and that this mechanism has as one of its components dopaminergic f bers that project up the medial fore-brain bundle from the midbrain to limbic and cortical regions. Evidence is reviewed that links both the reinforcing and locomotor-stimulating effects of both the psychomotor stimulants and the opiates to this brain mechanism. It is suggested that nicotine, caffeine, barbiturates, alcohol, benzodiaz-epines, cannabis, and phencyclidine----each ofwhich also has psychomotor stimulant actions--may activate the docaminergic f bers or their output circuitry. The role of physical dependence in addic-tion is suggested tovary from drug to drug and to be of secondary importance inthe understanding of compulsive drug self-administration. Attempts at a general theory of addiction are attempts to isr late--from a variety of irrelevant actionsmthose drug actions that are responsible for habitual, compulsive, nonmedical drug self-administration. The common assumption of addiction the-orists is that general principles of addiction can be learned from the study of one drug and that these principles will have heuris-tic value for the study of other drugs. Thus far, attempts at a general theory of addiction have failed to isolate common ac-tions that can account for addiction across the range of major drug classes. A major stumbling block has been the psychomo-tor stimulants--amphetamine a d cocainemwhich do not readily fit models traditionally based on depressant drug classes. The present article offers a new attempt at a general theory of addiction. It differs from earlier theories (e.g., Collier,