A limitation of our study was the relatively small sample size. Recent research has highlighted the importance of large sample sizes in promoting reliability and reproducibility of resting state fMRI research [47]. Given our relatively small sample size, our results should be interpreted with caution and treated as preliminary for hypothesis generation. Replication of our results is needed. Another limitation of our study was the heterogeneity of our OUD sample. While our heterogenous OUD sample may be more representative of the OUD population, it is unclear exactly how differences in treatment adherence, recency of drug use, and polysubstance use may influence functional connectivity. Future studies with larger sample sizes should examine the effects of these factors systematically. Additionally, our sample size was underpowered to determine group interactions with sex; further work is needed to analyze the influence of sex on functional connectivity in OUD. Additionally, there was a range of time lag between the date of assessment of OUD severity and the date of the MRI scan that may have led to inaccuracy in estimating the actual OUD severity at the time of the scan.
