Psychiatric Inpatients with Comorbid Cannabis, Cocaine Use Associated with Impulsivity

Gregory Larimer, MD, UT Health Medical School

Gregory Larimer, MD

A new study presented at the American Psychiatric Association’s 2018 Annual Meeting suggests that patients with cannabis use disorder and patients with cocaine use disorder may have different impulsivity profiles, especially in relation to attentional impulsiveness.

The study, conducted by researchers at UT Health McGovern Medical School, measured impulsivity amongst patients by using the Barratt Impulsiveness Scale (BIS-11) total score and subscales (attentional, motor and non-planning).

Previous studies have linked mood, psychotic and/or substance use disorders with significantly elevated levels of impulsiveness, however, there are limited data concerning impulsivity in cannabis users.

Researchers studied 184 psychiatric inpatients with a primary diagnosis of depressive disorder, bipolar related disorder, schizophrenia spectrum disorder or substance-induced disorder admitted to the same psychiatric unit at an academic psychiatric hospital in Houston, Texas.

Psychiatric inpatients ranged from 19—68 years old, with a mean age of 35.2. There were 102 (55.4%) male patients and 82 (45.6%) female patients. The group was comprised of 50% Non-Hispanic whites, 35.9% Blacks and 10% Hispanics.

On admission, patients submitted a urine drug screen (UDS) and were administered by a staff member, the BIS-11 and the National Institute on Drug Abuse (NIDA) Modified Assist-2.

The association of the UDS results and NIDA risk scores for cannabis versus non-cannabis users and cocaine users versus non-users were compared by BIS-11 scores and second order subscales.

On the NIDA, 60.3% (111) of the patients were positive for cannabis and 39.7% (73) positive for cocaine. On the UDS, 42% were positive cannabis and 19% cocaine.

A linear hierarchical regression was used in order to examine the association of the risk of substance use with the BIS total score and the BIS subscales (second order). Controlling for demographic factors, age and sex were entered first, followed by 3-second order subscale scores.

NIDA risk scores were used as independent variables.

Findings concluded the risk for cannabis cocaine use were significantly correlated with the total BIS-11 score, but also showed the association that BIS subscales differed between cocaine risk and cannabis risk.

Linear hierarchical regression revealed that the β coefficients for attentional (β= -.293, t= 2.135, p= 0.34) and non-planning impulsiveness (β= .397, t= 3.208, p= .002) scales were significantly correlated with risk of cannabis use, whereas only the non-planning BIS-11 subscale was significantly correlated with risk of cocaine use (β= .435 t= 3.427, p= 0.0001).

There were non-significant results found between BIS subscales and UDS results for both cocaine and cannabis, possibly because UDS results underrepresented the true number of substances users in the patient population due to a short window of time after use in which positive urine results were found. Additionally, there’s often a window of time between patients’ substance use and hospital arrival.

Total BIS-11 score and 2 out of 3 BIS-11 impulsivity trait subscale scores were significantly associated with risk of cannabis use.

The non-planning BIS-11 subscale was significantly associated with risk of cocaine use, while attentional and non-planning BIS-11 subscales significantly correlated with risk of cannabis use.

Patients with cannabis use disorder and cocaine use disorder may have different impulsivity profiles, especially with relation to differences in attentional impulsiveness.

Further research is needed to understand the underlying mechanism and relations between impulsivity and substance use.

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