Here's a good place to get started:
Psychological functioning of cocaine free-basers derived from objective psychological tests
Robert J. Craig, Ph.D. *
West Side Veterans Administration Medical Center Chicago, Illinois
*Correspondence to Robert J. Craig, (123), Drug Abuse Program, West Side VA Medical Center, 820 S. Damen Avenue, Chicago, Illinois 60612
This paper reports on two separate studies that compared cocaine free-basers with opiate addicts on objective personality tests (Adjective Checklist and MMPI). Both groups showed a similar organization of needs. While opiate addicts were characterized by acting-out traits, rebelliousness, depression, anxiety, alienation, and hyperactivity, the cocaine free-basers were characterized by similar traits, but at modulated levels of severity. Implications for treatment programs and for pharmacodynamic theories, with emphasis on the relationship between underlying personality structure and drug of choice, were discussed.
You will have to track the article down - but you can formulate some starting point from here.