Table 2.

Summary of results reported in systematic reviews for barriers of SUD treatment.

Level	Barriers a
Individual	Wrong belief about treatment: Belief that treatment was unnecessary (3, 8), preferring to withdraw alone without assistance (2, 8), beliefs about methadone (2, 10)
	Perceived fears: Fear of incarceration (4), Fear of stigma (4), Fear of inconvenience (4), Fear of loss custody of children (for mothers) (4), Fear of suspension or termination of parental rights (4), Fear of withdrawal symptoms (10), Fear of life without the stability and routine of taking methadone (10)
	Personal traits: Low self-esteem (10), Individuals’ self-concepts (10), Low self-confidence (10), Identity difficulties (10), Privacy concerns (2, 3, 8), Loneliness (10), Motivational factors (1, 3, 8, 9, 10). Poor coping styles to deal with difficulties (1, 5, 6) problem with emotional management (1, 10).
	Psychiatric comorbidities: (1, 3, 10)
Social	Stigma and lack of social support: Embarrassment or stigma (1, 2, 5, 8), Lack of social capital or social support (1, 3, 4, 5, 8), Not having anything else going on in one’s life (10)
	Family factors: Influence of habits of spouse/partner/family members/peers to drugs (6), Partner dropped out (10), Partners violence (10), No supportive family (1)
	Friends network: Non supportive friends (1), Difficulties with establishing a non-drug using network of friends, and severing ties with existing drug-using networks (10), Over-reliance on other clients (10) Secrecy or fear about the past in new interpersonal relations (10), Negative role model (10), Lack of models who have successfully recovered (10)
	Problems with a therapeutic team: None emphatic relationship from treatment staff (1, 2, 3, 4, 11), Poor therapeutic relationship between patients and practitioner (11), Tensions between peer workers and programme staff (5), Wrong belief about people who use drug among therapeutic team(5), Very dependent relationships with treatment staff (10), Clients’ passivity in accepting staffs’ attitudes (10)
Structural	Problems related to treatment provider services: Insufficient places (1, 2, 3, 8, 11), Waiting lists/times (2, 8, 11), Unsuitable/ineffective services for people with mental illness (1, 4, 8), Expensive costs and financial problems (8, 9, 11), Lack of available ancillary psychosocial services (10), Staff attitudes service providers (8), Lack of training in both nurses and General physicians(GPs) (11, 2), Lack of appropriate skill for non-physician team members for high-quality care (2, 10), A lack of primary care SUD fellowship (10), Lack of connection between emergency care and professional medical treatment (5). Insufficient training and support for peers (5) Lack of availability of peer workers (5), Lack of suitable treatment system for both genders (1, 2, 4, 8, 10, 11, 12), Ideology of treatment (9), Treatment intensity (10), Clinical inertia among nurses (11), GPs attitude to drug or alcohol (6), Therapeutic impasse (10), Failure to ground programming in the lived experiences of person who previously used drug (1, 2, 5), Lack of qualified workforce (2), The lack of appropriate treatment protocols (2), The preference for a forced detoxification approach instead of medical approach in some setting such as correctional-educational environments (2), Lack of adherence to treatment protocol (2).
	Legal barriers: Restrictive policies (lack of a legal structure for various organisational relationships, such as prisons and medical settings that patients could follow their treatment) (2), Implications for child custody arrangements for parents who use drug or alcohol (8), Misuse of prescribed medications (7, 10), Prescription challenges (10).
	Policy barriers: Exclusionary attitudes, policies and programmes (5), Policies which favour enforcement rather than harm reduction (5), Lack of focus on vulnerable sub-communities despite identified needs (5), No decision-making lived experiences of person who us drug (5) Failing to address social determinants of health (5), No considering contextual factors (5), Lack of focus during outreach on housing, jobs (5), The continued criminalisation of drug use (and people who use drugs) (5), Policies that favour enforcement (5, 1), Lack of linkage or coordination between correctional and community medications for treatment of opioid use disorder (MOUD) treatment providers (2).

^aThe below numbers in front of each facilitator refer to the first column, article number, in Table 1.