In an unlikely pairing, music and mental illness have been brought together in the powerful Melbourne Theatre Company performance of Next to Normal. The musical, which opens at the Arts Centre tonight, tells the story of suburban housewife Diana Goodman, who one day begins making her family's lunches and cannot stop. As the lunches pile up, she slowly realises she is losing her sanity and is suffering from bipolar disorder.

Playing alongside seasoned actors such as Kate Kendall and Matt Hetherington, actor Gareth Keegan, who plays Diana's son Gabe, says the musical challenges audiences to examine what normalcy and happiness means to them. "A lot of people who come to the play ask themselves what makes them happy. It's not just about having a nice house and car; it's about having nice friends, family and inner happiness," he says. Gareth's character has crucial influence on his mother Diana’s treatment and, ultimately, her confrontation of her illness. "I based Gabe on a snake because like a snake he can be very charming, but he's also very mischievous and like a shadow," he says. "He is extremely protective of his mother but he also has the power to hurt and heal."

Next to Normal has been showered with accolades including a Pulitzer Prize and three Tony Awards. This Australian version of the musical has innovated on the original off-Broadway performance. The set has been stripped back and now acts a metaphor for Diana's illness. "The set transports you to different locations in the play, whether it's the school or the doctor’s office," Gareth says. "It originates from the different fragments in the brain and is like a seventh character in the play."

The musical score also plays an important role in showing the emotional highs and lows experienced by Diana. "The different genres of music reflect where Diana's brain is at. I Miss the Mountains, for example, is quite grungy and rock because Diana knows the [medical] drugs are good but they stop her living," Gareth says. "Diana is very open about her mental illness and I think she represents the darkness that everyone is afraid to think of in society.”

The musical reaches a subject many audiences are uncomfortable confronting. Beyond Blue estimates a million Australians each year live with depression and two per cent of the population has bipolar disorder. The musical also brings to light a relatively unknown statistic that at least one third of young people of the Australian population have had an episode of mental illness by the age of 25 years.

Next to Normal has been placed on the year 12 drama syllabus and Gareth hopes the play will give young people in particular an outlet to discuss mental health. Amongst the heavy subject matter, Next to Normal emerges as a powerful musical where audiences will discover what ‘normal’ means to them. "The characters go through a cathartic experience and so does the audience,” Gareth says. There’s light at the end of the tunnel.

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Next to Normal is a Melbourne Theatre Company performance. It runs at the Playhouse, Arts Centre, from Tuesday May 3 to Saturday May 28.