The Marijuana Screening Inventory (MSI‐X): Reliability, Factor Structure, and Scoring Criteria with a Clinical Sample

OBJECTIVE

This study continues the psychometric evaluation of a 31-item Marijuana Screening Inventory (MSI-X) with adults referred to a substance abuse clinic, by determining MSI-X reliability, factor structure, scoring cutoff accuracy, sensitivity, and specificity with a DSM-IV-TR criterion measure.

METHOD

A "marijuana inventory" containing demographic, MSI-X, and DSM IV-TR diagnostic items was administered to 107 adults undergoing substance-use evaluation.

RESULTS

The MSI-X reliability was .90 with factor analysis deriving nine factors explaining 72.2% of the variance. Varimax rotation supports retention of all 31 items on nine factor-based scales. Receiver operating characteristic analysis determined MSI-X accuracy and cutoff points in relation to four DSM IV-TR diagnostic classifications. The MSI-X obtained the highest probability (.91) for accuracy in identifying both cannabis dependence and abuse, with six the optimal cutoff for maximum sensitivity (.83) and specificity (.89). Thus, MSI-X scores of > or = 6 are considered high risk. A cutoff score of 3 was associated with (probability, .90; sensitivity, .85; specificity, .81) identifying cannabis abuse only risk, providing a 3 to 5 score in the moderate risk range.

CONCLUSIONS

Clinical sample data supports the psychometric usefulness of the MSI-X as a screening tool. Marijuana lifetime use was 90% and past-year use 48%. The MSI-X identified 43% of lifetime users and 29% of past year users with moderate to high risk marijuana patterns deserving comprehensive evaluation. More males (15.9%) than females (7.5%) obtained MSI-X high-risk scores. The MSI-X empirically derived cutoff scores are within one point of the theoretical clinical cutoffs previously reported.

A Marijuana Screening Inventory (Experimental Version): Description and Preliminary Psychometric Properties

OBJECTIVE

Marijuana use prevalence, culturally confusing messages about marijuana risks, assessment dilemmas, and current screening inadequacies justify developing a marijuana specific screening inventory for assessment purposes. This article describes the Marijuana Screening Inventory (MSI-X) and its preliminary psychometric reliability, factor analyses, and factor structure.

METHOD

The MSI-X was administered to a community sample of 420 Army reservists participating in substance abuse educational classes. Participants responded anonymously to the 39-item MSI-X. SPSS analyses were performed with 408 returned MSI-Xs from a sample of 49% males and 40% females.

RESULTS

Analyses revealed 61% smoked marijuana during their lifetime. Reliability of the MSI-X was .89. Exploratory factor analyses of 31 scored items by principal components and varimax rotation supported a nine-factor structure, explaining 65.8% of the variance, with all items loading > or = .30. Within the sample, 7.84% scored > or = 7 suggesting "at risk" with marijuana; 6.12% scored 4 to 6 "suggestive of risk"; 20.83% scored 1 to 3 reflecting "normal or experimental" use; and 65.4% scored 0 suggesting "no problem."

CONCLUSIONS

The reliability, variance explained, factor-loading matrix of the nine-factor MSI-X structure and clinically predetermined scoring ranges appear useful for screening marijuana use patterns. Factor-based subscales were derived from the factor-loading matrix and described as a base for future confirmatory factor analysis. Although the MSI-X version needs psychometric strengthening, it shows potential as a marijuana-specific screening inventory for use in general mental health and primary care settings.