Contingency management significantly reduces stimulant drug use in dependent patients with serious mental illnesses, researchers report.
The team, from the University of Washington School of Medicine in Seattle, USA, also found that patients assigned to contingency management had fewer psychiatric symptoms and were less likely to be hospitalized during treatment than those who were not.
"If financial and other barriers to dissemination can be overcome, contingency management might be an effective adjunctive treatment for this population," comment Michael McDonell and colleagues in the American Journal of Psychiatry.
In total, 176 stimulant-dependent outpatients with schizophrenia, bipolar disorder, or other serious mental illnesses were randomly assigned to receive contingency management for stimulant abstinence plus treatment as usual (n=91), or treatment as usual only (n=85) for 3 months. They were followed up for a further 3 months.
The researchers found that participants in the contingency management group were less likely to complete treatment than those in the control group, at 42% versus 65%.
However, intention to treat analysis showed that patients in the contingency management group were a significant 2.4 times more likely to have stimulant-negative urine samples during the treatment period than controls.
Patients in the contingency management group were also 1.4 times more likely to have stimulant-negative urine samples during the follow-up period than controls, although the difference was not significant.
Furthermore, participants assigned to contingency management reported significantly fewer days of stimulant use during the treatment period (0.91 vs 4.67) and the follow-up period (1.83 vs 3.65) compared with controls.
Contingency management participants also had significantly lower psychiatric symptom scores on the Brief Symptom Inventory during treatment than controls (1.04 vs 1.24), as well as significantly lower ratings on the excitement subscale of the Positive and Negative Syndrome Scale (10.60 vs 11.69). The groups did not differ significantly on these measures during the follow-up period.
In addition, participants assigned to contingency management were significantly less likely to need psychiatric hospitalization during the entire study period compared with controls.
"Our results provide evidence that contingency management is an effective technique for reducing drug and alcohol use… psychiatric symptoms, and rates of inpatient hospitalization in seriously mentally ill adults," the researchers conclude.
They add: "Future research investigating the efficacy of contingency management in this population should focus on identifying strategies to improve treatment retention and exploring how contingency management might be optimally combined with other evidence-based interventions to further improve outcomes."
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