SUSAN NDINDA KIVUVA2026-05-042025-10https://repository.tangaza.ac.ke/handle/123456789/1606Substance use rehabilitation among individuals in recovery is significant to parents, peers, therapists and other stakeholders across the globe. Despite advances in addiction treatment, relapse rates remained extremely high in Langata sub-county. This study examined the relationship between personality functioning and relapse risk among substance use individuals undergoing treatment in Langata sub-county, Nairobi, Kenya. The objectives of the study were to examine the levels of personality functioning and relapse risk among substance use individuals undergoing treatment in Langata sub county, to investigate the relationship between personality functioning and relapse risk and to establish the significance of demographic characteristics of age, gender, marital status, admission criteria and relapse risk. The study was grounded by Interpersonal theory and Relapse prevention theory. The study employed a correlational research design, with a target population of 144 individuals. The Census method was used to include the whole population, giving a sample size of 144 participants. This study utilized two standardized tools, the Levels of Personality Functioning Scale (LPFS) and the Stimulant Relapse Risk Scale (SRRS), to collect data. The data was analyzed using descriptive statistics (percentages, frequencies) and inferential statistics and particularly Pearson Correlation coefficient, t-test and One Way ANOVA. The results showed that 57.6% (72 respondents) scored on category of healthy functioning. There were 15.2% (19 respondents) who scored on the category of mild or subclinical level of personality functioning, 12% (15 respondents) fell into the category of clinically dysfunctional and 5.6% (7 respondents) were severely dysfunctional and 9.6% (12 respondents) were extremely dysfunctional. Furthermore, the results showed that 2.4% (3 respondents) were in the category of low level of stimulant relapse risk. There were 56.8% (71 respondents) who were in the category of moderate level of stimulant relapse. There were 40.8% (51 respondents) who scored in category of high level of stimulant relapse risk. Moreover, the results showed strong positive relationship (n = 125, r = .683, p = .000) between personality functioning and stimulant relapse risk among the substance use addicts. Finally, there was a significant difference between demographic characteristics and relapse risk. There was a significant difference in the scores for relapse risk between Male (M = 98.11, SD = 28.24) and Female participants (M = 113.00, SD = 32.47) at conditions, t (123) =. -2.21, p = .03. The results showed that there was significance difference between age and relapse risk (r = .434, p. ≥ .05). Also, the results showed there was a significant difference between marital status and relapse risk (r = .013, p. ≥ .05). The descriptive statistics emerging from the results suggested that there was a significant difference in the scores for relapse risk between Voluntary (M = 98.22, SD = 26.49) and Involuntary participants (M = 103.36, SD = 32.44) at conditions t (123) =.052, p = .033. The study recommended that addiction counselors to tailor individualized treatment plan for each client in line with their personality functioning and levels of risk of relapse.enThesis