Several neurobiological factors are related to opiate-use disorder (OUD), and among them, neurotrophins have a relevant role. Brain-derived neurotrophic factor (BDNF) is a central neurotrophin involved in many neuronal processes, and it has been related to several psychiatric diseases and addictive disorders. BDNF can be measured in plasma and serum; its levels may reflect BDNF concentrations in the central nervous system (CNS) and, indirectly, CNS processes. Hence, peripheral BDNF could be a biomarker in clinical practice. This manuscript explores the findings about peripheral BDNF and OUD in humans. Opiates induce neurotoxicity in the CNS, which may be correlated with modifications in BDNF expression. Thus, basal levels of peripheral BDNF in OUD patients may be altered, which could be modified with abstinence. Also, opiates may modify epigenetic processes that may be associated with peripheral concentrations of BDNF, and in this line, withdrawal could reflect recovering processes in the CNS. Additionally, treatment modifies the peripheral concentrations of BDNF, but the clinical implications of those changes are yet not elucidated. No specific conclusion can be performed and more investigation in this area is necessary to elucidate the real potential of peripheral BDNF as a biomarker.

Introduction: COVID-19 has had a great impact on mental health in the general population. However, few studies have focused on patients with substance use disorders (SUDs). This research aimed to compare the clinical status and substance use patterns of SUD outpatients, before and during confinement due to the COVID-19 pandemic. Methods: This multicentre study recruited 588 patients (29.2% women; M age = 47.4 ± 11.7 years) in thirteen centres for addiction treatment in Catalonia, Spain. All subjects were evaluated with validated instruments and ad hoc questionnaires. The sample was divided into 3 groups according to how the substance consumption pattern changed during lockdown (maintained pattern, worsened pattern, and improved pattern). Results: More than 62% of the patients maintained or worsened their consumption pattern during confinement, and about 38% improved throughout this time. Diverse factors were associated with the changes in pattern like age, addiction severity, psychological distress during lockdown, social and familial issues, and therapeutic variables. Conclusion: The home lockdown during the COVID-19 pandemic was associated with major implications for substance consumption and psychiatric distress among SUD outpatients. Considering this, the need to plan appropriate interventions in cases of similar health crises is highlighted.