From Dr Melfi in The Sopranos, to Betty Draper in Mad Men, using therapy sessions to reveal what makes fictional characters tick has become one of television's favourite dramatic devices. Cable network HBO's latest success, In Treatment, centres on the conversations between doctor and patient in real time, five nights a week in half-hour sessions, and has earned a Golden Globe acting award for Gabriel Byrne.

In the central role of psychiatrist Dr Paul Weston, Byrne gives a subtly nuanced performance. His is a kind and reassuring presence, exuding calm and gentle concern for his troubled patients – except, that is, on Friday's episodes when the scenes take place in the office of Weston's own therapist and the counsellor becomes the client. His inner conflicts are revealed; he becomes the one who is aggressive and vulnerable by turns. The acting is such that it doesn't seem like acting at all – viewers feel like they are eavesdropping on real conversations.

If In Treatment feels more like a documentary than a drama, Byrne's own documentary, Stories From Home, screened at last year's Galway Film Fleadh, candidly revealed the demons this otherwise intensely private actor has dealt with since childhood. On other occasions too, he has spoken of abuse from age eight to 12 at his Christian Brothers primary school.

"There were things like being lifted off the ground by the hair of your head and being beaten with chair legs. One guy was held out of the window by his leg. It was accepted because a child doesn't have the critical apparatus to examine a situation like that," he recalled in a London Times interview. He is reluctant to "carp on about it" and yet recognises that, while he didn't suffer physically, "the damage was emotional, and that took me a long time to shake off".

Cycles of drink and depression were broken when he decided to seek treatment, calling it "one of the most difficult things ever in my life". That was a few years back and he says now that he doesn't miss drinking.

"I used to drink to get out of depression, which led to more depression. It was a vicious circle. I still have to be careful with depression. It's about trying not to let other people know all you want to do is lie in a corner and have nothing to do with anyone."

While those journeys to dark places and back in his emotional life may or may not feed into his acting, Byrne has certainly moved around a lot in the physical sense during his 58 years, having lived in Spain, London, New York and Los Angeles. Before finally focusing on acting as a career at the age of 29, he had already amassed a diverse CV.

After training for the priesthood at an English seminary, he returned to Dublin a confirmed atheist, aged just 15, and worked first as a post office messenger boy, then as a waiter in what was then the capital's only gay bar, as an apprentice chef, in a morgue, as a bicycle repairer, selling encylopaedias and as "the worst plumber in Dublin".

It all led to a conviction that college would be a better option. Archaeology and linguistics were his chosen studies at University College Dublin, and he became particularly fluent in Irish – a talent that later resulted in writing his drama Draíocht for TG4 in 1996.

His stage career started with the Focus Theatre and the Abbey, followed by the Royal Court Theatre and the Royal National Theatre in London. He is remembered particularly from those times for his television roles in the long-running The Riordans, and then his own spin-off series in the eponymous Bracken.

Galloping through the bracken was to prove his first film role as Lord Uther Pendragon in John Boorman's Excalibur, filmed here in 1981. Since then, Byrne has become a Hollywood name, but often opting for films that earn cult status rather than box-office acclaim, such as The Usual Suspects or the Coen Brothers' Miller's Crossing.

In 1999, the almost-priest played an actual priest in Stigmata – and then played Satan in End of Days. Like many leading men, his name has inevitably carried the 'romantically-linked' tag with leading actresses such as Julia Ormond, his co-star in Smilla's Sense of Snow.

He is dismissive of references to his romantic appeal. "I've never really thought about myself that way or been conscious of it. I've never really been cast in 'out and out' romantic roles."

He had a 12-year relationship with the late film producer áine O'Connor, followed by his six-year marriage to actress Ellen Barkin. His move to live in New York at the age of 37 was down to the love affair with Barkin. The couple divorced in l993.

Fatherhood, he has said, is something he takes very seriously. "There's a raw honesty about kids. I think the unconditional love that flows between parents and kids is the most beautiful thing. It teaches you your place in the world."

His place now is very much New York, in a period brownstone in Brooklyn. With his native city, it's more of a love/hate relationship.

"In Dublin, I'm constantly defined by my past," he has said. "In New York, I have a clean slate."

He is a spokesperson for the Irish Hospice Foundation, while also an outspoken critic of the country's health service. He also takes his role as a Brooklyn citizen very seriously and is currently battling with New York property developers over their plans to erect a tower block in that part of the district referred to as Dumbo (down under the Manhattan Bridge overpass).

Although he lives in a city famous for its neurosis, it's only lately that Byrne himself decided to do the New York thing and embrace therapy. "I found that my resistance to it was based on old thinking, that talking about yourself and trying to find out who you are and talking about your childhood was all just American self-indulgence."

For the would-be priest who once saw his role in life as hearing the confessions of others, it's an intriguing conclusion.

His most famous fictional character to date, psychiatrist Paul Weston, would surely agree.

CV

Born: May 1950, Drimnagh, Dublin to Dan, a cooper, and Eileen, a nurse

Educated UCD, studying archaeology and linguistics

Career Over 35 films including Miller's Crossing and The Usual Suspects

Personal life Two children with ex-wife Ellen Barkin. Lives in New York with partner, actress Anna George

In the news For his Golden Globe-winning performance in In Treatment