A Double-Blind Randomized Controlled Trial in Effectiveness of Parent-Child Interaction Therapy on Psychological Indicator and Cortisol Level in Children of Caregiver with Cancer

High-potency Cannabis (HPC) is commonly used by patients with cancer to relieve pain. Parents’ HPC consumption can have an adverse effect on the physical, psychological, and social aspects of children. This study was conducted aimed to investigate the effectiveness of parent-child interaction therapy (PCIT) on the reduction of aggression and cortisol level in children of dependent cannabis caregiver with cancer. In a double-blind randomized controlled trial, from March 2015 to October 2016, 50 caregivers residing in Tehran, Iran with metastatic cancer consuming HPC and their children with aggression problem were selected, using respondent-driven sampling (RDS) method and were randomly assigned to the experimental or control groups through block randomization. Changes in the level of aggression and cortisol during 12 weeks were analyzed by repeated measures correlation (rmcorr) and generalized estimation equation (GEE) through SPSS 22 software. Statistical significance was accepted at P < 0.01. The primary outcomes showed that 12 weeks of PCIT had a significant effect on the reduction of children’s aggression and the level of salivary cortisol in children (P < 0.01). However, the results were not stable until the follow-up stage (P = 0.067). Secondary outcomes showed that there was a significant relationship between aggression index and cortisol level (P < 0.01). The findings of the present study are consistent with the research background confirming the role of systematic and nonlinear (cyclic) look at behavioral and psychological problems during growth. These findings can be found in family setting and in educational settings such as kindergartens with clinical application.