Efficacy of Acceptance and Commitment Therapy on Substance use Disorders Among Patients in Selected Rehabilitation Centres in Nairobi County, Kenya

Abstract

The increasing prevalence of Substance Use Disorders (SUDs) has become an emerging public health concern in Kenya, contributing to the global addiction crisis and straining healthcare systems and communities. This study assessed the effectiveness of Acceptance and Commitment Therapy (ACT) on SUDs among patients in selected rehabilitation centres in Nairobi County. Specifically, it assessed the prevalence of different types of SUDs; the relationship between socio-demographic variables and SUDs; the risk levels of SUDs; the comorbidity of SUDs; and evaluated the efficacy of ACT in treating patients with SUDs. The study was guided by, the Psychological Flexibility Model and Self-Efficacy Theory. A quasi-experimental research design was employed, involving an experimental group that received ACT and a control group that received Treatment as Usual (TAU). Six rehabilitation centres were selected using purposive sampling. A total of 100 male patients aged 18–59 years were then recruited through convenience sampling. Data collection tools included a socio-demographic questionnaire, the Acceptance and Action Questionnaire-II (AAQ-II), the Alcohol, Smoking, and Substance Involvement Screening Test (ASSIST), the Beck Depression and Anxiety Inventories (BDI and BAI). Data were analyzed using the Statistical Package for the Social Sciences (SPSS v.25). Descriptive statistics summarized substance use prevalence and socio-demographic characteristics. Chi-square tests and one-way ANOVA assessed associations between demographic variables and SUD prevalence and risk levels. Chi-square test was used to examined relationships between substance use and mental health symptoms, while repeated measures ANOVA tested the impact of ACT over time. The findings revealed a high prevalence of different types of lifetime substance use, with alcohol (96%), tobacco (74%), and cannabis (62%) being the most commonly used substances. Use of sedatives (25%), opioids (11%), inhalants (10%), and other substances such as khat (10%), cocaine (9%), amphetamines (7%), and hallucinogens (6%) was also reported, though at lower levels. Moderate to high-risk substance use levels were observed, especially among younger participants. Socio-demographic variables such as income, education, employment, age, and religion showed significant associations with both SUD prevalence and risk levels. Additionally, mild to high levels of comorbid depression and anxiety were reported. The study found that ACT significantly reduced symptoms of comorbid depression and anxiety over time, with large effect sizes observed for anxiety (Wilks’Lambda= .727, F(2, 90)=16.89, p<.001,η² = .273). A significant linear decline in depression symptoms (Wilks’Lambda= .852, F(2, 90) = 7.82, p < .001, η² = .148), were also observed. Remarkably, the ACT intervention led to significant reductions in psychological inflexibility (Wilks’Lambda= .673, F(2, 90)=21.87, p<.001,η² = .327). and substance use severity across the study period (Wilks’Lambda= .705, F(2, 90)=18.64, p<.001,η² = .295)., while the control group showed minimal change. In conclusion, the study provides empirical support for the effectiveness of ACT in treating SUDs and addressing co-occurring mental health challenges in rehabilitation settings. The findings also underscore the need to consider socio-demographic determinants and integrate mental health services into substance use treatment. These insights may inform clinical practice, mental health policy, and future research on culturally adapted interventions in Kenya and similar settings.