The 27-year-old, who played Seamus Finnegan in the boy wizard films, has revealed he kept his thoughts to himself because he was afraid no one would understand what he was going through.

Devon admits at his lowest, he started to contemplate suicide - even though he was enjoying success as a child star.

"I remember feeling very low on my 16th birthday," he told RTE 2fm's Eoghan MCDermott. "I was staying in a fantastic suite in a hotel in London. I'd celebrated my birthday the day before on set. My room was full of gifts and I should have been happy but I wasn't."

His mental health went downhill from there as homesickness crept in while he was making the Potter films in the U.K.

And then he was diagnosed with Bell's Palsy during filming of Harry Potter & the Order of the Phoenix. The condition temporarily paralysed one side of his face and destroyed his confidence.

"I didn't want to leave the house," he said. "I didn't want people to see how I looked. I didn't want them to see how I felt."

Devon then turned his back on his friends and began collecting horses to sell, spending his days at the stables to distract him from his suicidal thoughts.

"I was just a mess, I didn't know whether I was coming or going," he recalled. "I had let down my parents. I couldn't do anything right."

And then one evening, he came close to ending his life, adding, "I had a rope and threw it over one of the banisters in the barn and was pretty much getting ready to hang myself."

The scary moment dragged the actor back to life and he reached out to his parents for help, explaining what he had been going through. He discovered his mother had also battled depression.

"I completely regret not talking about it before," Devon added. "I wish I'd been open when I was 16. I'd have had a much better life."

Now, he's speaking out in the hope he can encourage others to seek help before depression ruins their life, and he took to Twitter on World Mental Health Day (10Oct16) to help raise awareness of mental health issues.

He told one fan that he is now "in a good place" doing the things he once avoided in an effort to improve his confidence.