Pop singer Justin Bieber has opened up about his personal torments since becoming a global star at 13.

The 25-year-old singer has posted a lengthy note into how he tried to cope with fame and said that he became involved with "pretty heavy drugs" as a teenager, reports mirror.co.uk.

Posting on Instagram, Bieber wrote: "It's hard to get out of bed in the morning with the right attitude when you are overwhelmed with your life your past, job, responsibilities, emotions, your family, finances, your relationships.

"When it feels like there's trouble after trouble after trouble. You start foreseeing the day through lenses of "dread" and anticipate another bad day."

The "I'm the one" crooner said that he had to "battle suicidal thoughts" in the past.

"I am fortunate to have people I'm life that continue encourage me to keep going (sic.)."

He then talked about how he had turned to drugs when in his late teens he tried to cope with the strains of fame.

"I started doing pretty heavy drugs at 19 and abused all of my relationships. I became resentful, disrespectful to women, and angry. I became distant to everyone who loved me, and I was hiding behind, a shell of a person that I had become. I felt like I could never turn it around," he wrote.

Bieber says it has taken him years to bounce back from all the "terrible decisions".

"Fix broken relationships, and change relationship habits. Luckily god blessed me with extraordinary people who love me for me."

Beiber was discovered while performing on YouTube aged 13 and soon amassed millions of fans but had several run-ins with the law and often made headlines for his controversial behaviour rather than his music.