Opioid dependency remains a worldwide crisis and treatments aimed at abstinence and recovery are mainly ineffective with high relapse rates. There is mounting evidence that social deficits and emotional co-morbid impairments negatively impact recovery from opioid dependency following detoxification and constitute a motivational trigger to relapse.

This work aimed to identify risk and protective factors for relapse to opioid misuse following the start of treatment. Given the emergence of preclinical and clinical data showing anti-addictive properties of neuropeptide oxytocin, a randomised double-blind placebo-controlled pilot trial was performed to investigate the efficacy of intranasal oxytocin in preventing relapse in post-detoxified opioid-dependent individuals. This work also investigated the efficacy of intranasal oxytocin in reducing opioid craving, anxiety, depression, social anxiety and sleep disturbances while enhancing social cognition and quality of life in these individuals.

The results described in this thesis show that inpatient psychosocial support was a protective factor against relapse, compared to a community centre treatment program. Also, remaining in and completing a treatment program was protective against relapse. The pilot trial did not complete due issues with the supply of oxytocin. Two participants were administered intranasal oxytocin over 2 treatment days, and showed reduced anxiety and social anxiety, improved sociability, improved mood, increased trustworthiness, decreased hostility and decreased subjective withdrawal symptoms with reduced sleep disturbances, compared to baseline. This thesis also provides a reflective analysis on the difficulties in recruiting and working with vulnerable participants as well as the challenges of setting up and running a clinical trial of an investigative medicinal product, within the NHS. The work suggests some changes to be implemented for a successful clinical trial.

Given these results and the evidence for anti-addiction and pro-social properties of oxytocin, future studies would direct attention to oxytocin-based treatment programs, looking to engage addicts in psychosocial treatment programmes.