Devon Murray, the Irish actor who played Seamus Finnigan in the Harry Potter films, says he's been "battling depression".
He posted online that it has been something he's been going through for the past 10 years.
Earlier this year he had "suicidal thoughts", he says, and encouraged more people to talk about.
In April, the 27-year-old was forced to pay his former agent 260,000 euros (£210,000) in unpaid commission.
The high court judge said he was sorry some of his earnings, close to a million euros, went on pursuits that "were not helpful".
Devon's mum had claimed during the proceedings that he'd "gone out drinking, taken out girls and bought cars, because that is what teenage boys do".
World Mental Health Day is on 10 October every year, to help raise awareness of mental health issues.
The actor says he's felt "so much better" having asked for help and speaking out about his mental health problems.
He also commented that "winter time is always the worst" in a response to a fan who praised him for speaking out.
Devon asked for his fans to take care of friends and family.