Smoking can increase depression risk, according to a new Kiwi study.
The study, conducted by Otago University, suggests nicotine-dependent people are more than twice as likely to get depressed as those who don't smoke.
Researchers from the university's Christchurch Health and Development Study quizzed over 1000 people about their smoking habits and symptoms of depression at ages 18, 21 and 25 to come up with their conclusion.
"Our findings are consistent with the conclusion that there is a cause and effect relationship between smoking and depression, in which cigarette smoking increases the risk of developing symptoms of depression," Stuff.co.nz quoted lead researcher David Fergusson, as saying.
He added: "The reasons for this relationship are not clear. However, it's possible that nicotine causes changes to neurotransmitter activity in the brain, leading to an increased risk of depression."
The study has appeared in the British Journal of Psychiatry.