Aim & Objective:
Impact of exposure of smoking on mental health conditions is well studied, but not of second hand smoke exposure. This is an attempt to find the association between second hand smoke exposure and depression.

Methods:
A systematic search was conducted for published studies in English till June 2017. Independent two electronic searches were carried out in Medline, IndMED using key words “second hand smoking”, “passive smoking”, “environmental tobacco smoke” & “depression”. We have included articles reporting adjusted relative risk (RR) or odds ratio. References of the selected articles were also traced. Meta-analysis was performed to calculate pooled estimate using random effects model.

Results:
We have got 165 records from searched databases. Of which, 20 records were included for full text review after screening abstract and removing duplicates. Finally, fifteen articles were included for meta-analysis. Second hand smoke exposure exposure was found to be associated with depression (RR=1.37, 95 CI: 1.26, 1.48) with heterogeneity, I2: 83%.

Conclusions:
We have found modest strength of association for second hand smoke exposure and depression. Unknown confounders might have reduced the pooled estimate in the longitudinal studies.