Introduction:
Worsening youth mental health has been an increasing public health concern particularly during Covid-19. Associations between mental health problems (MHP) and tobacco use are well-established and linked with inequalities but whether similar patterns exist for e-cigarette use is less clear.

Objective:
We examine smoking and e-cigarette use in Irish 20 years olds with doctor-diagnosed MHP.

Material and Methods:
We use data from 5,190, 20 year-olds from Wave 4 of Growing Up in Ireland Child Cohort, the national longitudinal study of children and young people. MHP were assessed using 20-year-olds’ self-reports who had been diagnosed by a doctor, psychologist, or psychiatrist. Young adults also self-reported their ever and current smoking, and ever and current use of e-cigarettes. Frequencies and cross-tabulations analyses were performed using STATA version 16.1.

Results:
Among Irish 20-year-olds, 19.4% (n=1,008) reported having been diagnosed with a MHP. The majority of these (n=949) reported depression or anxiety. Young adults with MHPs reported higher prevalence for all measures of smoking and e-cigarette use than did those without MHP, and findings were statistically significant for all 4 measures. Almost half of those with MHP were current smokers (47%; n=474 vs. 35.2%; n=1472 without MHP). Almost four out of five were ever-smokers (78.3%; n=789 vs. 72.8%; n=3018). E-cigarette ever-use was 56.9% (n=574) compared with 45.5% (n=1886) in those without MHP and e-cigarette current use was 16.6% (n=168) compared with 12.5% (n=522).

Conclusions:
Among young adults, similar associations with MHP exist for e-cigarette use as have been shown to exist for smoking. Our data do not include other mental health problems not reported or not doctor-diagnosed. However, for 20 year-olds with depression and anxiety, a need exists for education and cessation interventions to address their significantly higher rates of smoking and e-cigarette use which likely exacerbate further the health inequalities among this vulnerable group.