Predictive utility and measurement properties of the Strength of Implementation Intentions Scale (SIIS) for condom use.

BACKGROUND: Implementation intentions are situation-linked action plans that increase health behaviors such as condom use. Few studies have measured the strength of implementation intentions, especially regarding condom use. Non-injection drug users are at high risk for HIV due to risky sexual practices. Substance use before sex may increase risky sexual behaviors, and implementation intentions are a promising, practical route for HIV prevention.

PURPOSE: This prospective study assessed the measurement properties of the newly developed Strength of Implementation Intentions Scale (SIIS) for condom use and investigated whether the SIIS predicted condom use one-year later. The study evaluated whether behavioral intentions and alcohol or methamphetamine use before sex modified the relationship between the SIIS and condom use.

METHODS: Participants were 590 non-injection drug users convicted of nonviolent drug offenses in court-mandated outpatient drug diversion programs. They completed self-directed computer assessments at baseline and at one-year follow-up. Measures included demographics, behavioral intentions to use condoms, the SIIS for condom use, alcohol and methamphetamine use before or during sex, and condom use. Psychometric properties, direct, and interaction effects of the SIIS were evaluated using structural equation modeling and general linear regressions.

RESULTS: The SIIS, behavioral intentions, and condom use were positively correlated and there was discriminant validity between all three constructs. In addition, the SIIS predicted condom use one-year later in this high-risk population. No significant interactions were detected.

CONCLUSIONS: The SIIS is predictive of condom use behavior, is psychometrically sound and distinct from behavioral intentions, and can be incorporated into HIV prevention interventions and used as a mediator variable. In addition, it can be used as an outcome measure where a follow-up is not feasible. The SIIS can also be tailored for additional HIV-related behaviors such as HIV-testing, adhering to antiretroviral medication, prescribing and adhering to pre-exposure prophylaxis, and other health behaviors.