How do medical and non-medical use of z-drugs relate to psychological distress and the use of other depressant drugs?

•3.8% of the Americans (12 million) used a z-drug in the past year.•Z-drug medical and non-medical use are associated with psychological distress.•Z-drug use is highly correlated with BZD use, misuse, and use disorders.•Z-drug use is related to use and dependence of marijuana and alcohol.•Distress may confound the relation between z-drugs and BZD, alcohol, and marijuana. Z-drugs are hypnotic drugs used for insomnia with considerable potential of abuse. We investigated the relationship of past-year medical and non-medical use of z-drugs with past-year: i) psychological distress; ii) medical use, non-medical use, and DSM-IV use disorder of Benzodiazepine (BZD) tranquilizers; iii) use and DSM-IV alcohol and marijuana use disorders, recreational drugs with a depressant effect on the central nervous system. Data came from the 2015–2017 NSDUH (n = 128,740). Participants aged 18+ were asked if they had used any Z-Drug medically or non-medically in the past year. We investigated the associations between the three-level z-drugs variable with psychological distress and BZD, alcohol, and marijuana variables in multinomial logistic regression models. Past-year prevalences of z-drug use were 3.3% for medical and 0.5% for non-medical use. Medical and non-medical users of z-drugs had higher risk of psychological distress, compared to non-users. Medical and non-medical users of z-drugs had higher risk of medical use, non-medical use, and BZD use disorders. Compared to non-users of z-drugs, medical users had higher risk of marijuana and alcohol use and alcohol use disorders, while non-medical users had higher risk of marijuana use and marijuana use disorders and alcohol. Z-drug users have elevated risk of use and dependence of BZDs and recreational drugs, possibly due to concurrent prescribing and self-medication.