Horizon airs on BBC2 tonight (2 May) BBC

A new BBC2 programme, Horizon, will delve into the minds of people diagnosed with symptoms such as hearing voices, paranoia and hallucinations.

The second part of the show's title – Why Did I Go Mad? – seems a rather blunt start to what seems to be a touchy subject. The title is in stark contrast to Heads Together, which embodies the royals – Princes William and Harry and Kate Middleton – recent efforts to ban the stigma surrounding mental health.

The show is part of the BBC's Mental Health season following the two-part documentary Mind Over Marathon in April. It takes a deeper look into serious conditions such as schizophrenia and psychosis and scientific advancements in treatment.

Reflecting on centuries-old psychiatric notions, it looks at why physicians treated voices and hallucinations as an enemy and something to be feared and quashed. As attitudes have changed towards mental health in recent years, new ways of understanding the human mind have led to an evolution in treatment.

The programme follows three individuals experiencing a variety of symptoms, from hearing voices, hallucinations and paranoia. It explores possible causes and what it is like to live on a day-to-day basis with manifestations that led society to once label folk as 'insane'.

One such sufferer is Rachel Waddingham, who has a part time job at the NHS working with people in crisis. It is hard to believe that the bubbly 39-year-old has been diagnosed with schizophrenia.

She says in the show: "My life feels mostly awesome. I get stunned by it sometimes, all the little mosaic pieces. I still struggle a lot, and I've got a lot to understand about the things I go through. It's not like I'm super-wise – but maybe, one day, I will be."

Horizon: Why Did I Go Mad? airs tonight (2 May) at 9pm on BBC2.