Problematic internet use, especially in people with substance use disorder, may negatively affect their quality of life (QoL). However, it is unclear whether sleep quality is a key mediator in the association between problematic internet use and QoL among people with substance use disorder.

This study aimed to investigate the relationship between problematic internet use and QoL and how sleep quality may mediate the association between these two variables.

Overall, 319 people (85% male) with substance use disorder (mean age 42.2 years, s.d. 8.9) participated in a cross-sectional study in Taiwan. The Smartphone Application-Based Addiction Scale, Bergan Social Media Addiction Scale, Internet Gaming Disorder-Short Form, Pittsburgh Sleep Quality Index and World Health Organization Quality of Life Questionnaire Brief Version were used.

The prevalence of sleep problems was 56%. There were significant and direct associations between sleep quality and two types of problematic internet use, and between sleep quality and different dimensions of QoL. All types of problematic internet use were significantly and negatively correlated with QoL. Mediated effects of sleep quality in relationships between the different types of problematic internet use and all dimensions of QoL were significant, except for problematic use of social media.

Different types of problematic internet use in people with substance use disorder may be directly associated with reduced QoL. Sleep quality as a significant mediator in this association may be an underlying mechanism to explain pathways between problematic internet use and QoL in this population.

Cancer is a leading cause of death worldwide. Religiosity is a factor that may help cancer patients to cope with their disease. The aim of the current study was to validate a Persian translation of the Muslim Religiosity Scale (MRS) in a population of Iranian patients with cancer.

Two thousand patients were invited to participate in this multisite study, of whom 1,879 participated. Patients completed a demographic questionnaire, the MRS, and several scales, including the Patient Health Questionnaire–9, the Hospital Anxiety and Depression Scale, the Perceived Social Support Scale, and the SF–12 quality of life measure. Backward–forward translation was employed to develop a Persian-language version of the MRS. Cronbach's alpha and two-week test–retest reliability were also assessed. Convergent and discriminative validity as well as the factor structure of the scale were also examined.

The internal reliability (α) of the religious practices and beliefs subscales was 0.88 and 0.92, respectively. The intraclass correlation coefficient (ICC) was 0.92 (range = 0.75–1.0). The scale demonstrated solid convergent and discriminative validity. Factor analysis indicated two main factors, as predicted, with an appropriate goodness of fit (χ2 = 76.23, RMSEA = 0.065). Such factors as marital status, quality of life, social support, and self-efficacy were positively associated with MRS total score, while anxiety, depression, and suicide ideation had negative associations.

The MRS is a useful tool for assessing religiosity in Iranian patients with cancer and is associated with a number of important health outcomes.