Highlights of Recently Published NIDA-Supported Studies

Court Mandates Help Men With Antisocial Personality Disorders Stay in Treatment

Men with co-occurring substance abuse and antisocial personality disorders may particularly benefit from judicially mandated addiction treatment. Such legal pressure has been shown to exert a positive effect on treatment retention in a general population of drug abusers (see What the Numbers Say).

Dr. Stacey B. Daughters and colleagues at the University of Maryland recently studied 236 men who began therapy for substance abuse problems. Ninety-three of the men met standard criteria for antisocial personality disorder (ASPD), a condition characterized by chronic behavior problems, deceitfulness, and lack of conscience and regard for others.

Among men without ASPD, 85 percent remained in therapy whether the treatment was voluntary or mandated. However, the investigators found that among men with ASPD, about 94 percent of those who were legally required to participate in residential substance abuse treatment remained for a month, compared with just 63 percent of those who had volunteered to enter treatment.

Although ASPD is rare in the general population, researchers estimate that 40 to 50 percent of people in drug treatment programs have the disorder. Moreover, prior research suggests that ASPD increases the risk for addiction treatment dropout, relapse, and, among those with jail sentences, a return to criminal behavior.

The Maryland team's findings have two important implications for substance abusers with ASPD: Judicial mandates offer a way to keep them in addiction treatment programs, and voluntary participants may require special interventions to keep them actively engaged in therapy.
Journal of Substance Abuse Treatment 34(2):157-164, 2008. [Abstract]

New Tracer for Nicotinic Receptors Promises Improved Specificity

Researchers at NIDA's Intramural Research Program have developed a radiolabeled compound for animal studies of nicotinic acetylcholine receptors in the brain. Tests in monkeys indicate that the new tracer readily enters the animals' brains and binds primarily to the nicotinic receptor subtype called α4β2*. These receptors play a role in nicotine addiction and have been implicated in other neurological conditions, including dementia, epilepsy, depression, and anxiety.

In brain regions containing these receptors, the new radiotracer's accumulation is greater than that of 2FA, the tracer currently used in human imaging studies. As a result, the new tracer produces sharper and more detailed positron emission tomography images and may be especially useful for studying α4β2* nicotinic receptors in brain areas where they are sparsely distributed. The specificity of the new radiotracer accumulation for the regions with these receptors is three- to four-fold that of 2FA, and tests in mice indicate that the new compound is equally safe, says Dr. Alexey G. Mukhin, now at Duke University in Durham, North Carolina.

If further animal and human imaging research confirms these results, the tracer could advance the study of the relationships between α4β2* receptors and specific aspects of nicotine addiction and promote the development of medications for a wide variety of disorders. The chemical name for the new tracer is 6-chloro-3-((2-(S)-azetidinyl)methoxy)-5-(2-fluoropyridin-4-yl)pyridine ([18F]NIDA522131).
Journal of Neurochemistry 104(2):306-315, 2008. [Abstract]

Adolescent Rats Self-Administer More Nicotine Than Adults

Studies comparing adolescent and adult rats have added to the evidence that the adolescent brain is particularly vulnerable to nicotine addiction. Dr. Edward D. Levin and colleagues at the Duke University Medical Center allowed male rats not previously exposed to nicotine to self-administer the drug for 4 weeks. During the first 2 weeks, the 13 adolescent rats took more than three times as much nicotine as the 13 adults. Nicotine consumption decreased as the adolescents matured, and it reached adultlike levels by the end of week 4.

In a prior study with female rats, the researchers found that adolescents self-administered twice as much nicotine as adults. Unlike the male rats in the current study, however, as the adolescent female rats matured, they continued to self-administer more nicotine than adults. Taken together, the team's results suggest that adolescent male rats may initially be more sensitive than females to nicotine, but females may experience a more persistent vulnerability.
Neurotoxicology and Teratology 29(4):458-465, 2007. [Abstract]

Volume 22, Number 3 (April 2009)