I KNOW two serious meditation practitioners. Half an hour after the first told me meditation gave him a calm and balanced mind, I heard that the second had been committed to a mental hospital.

Passing paramedics spotted my flatmate meditating on the footpath of Swanston Street and called the police. Recently he had been suffering from psychosis tinged with Buddhist altruism and had come to the conclusion that moving through the world ‘killed molecules’. He would suddenly freeze, mid-stride, to avoid colliding with nearby atoms. When the police found him he was rooted to the sidewalk, gawking at his own shadow.

I didn’t find out about his episode until returning from an interview with Mr Siladasa, the chairman of Melbourne Buddhists Centre, days later. During the session Siladasa, a respected neurologist, had spoken eloquently about the benefits of meditation. He was lucid, logical, sane and happy. How could the same technique have contributed to both mental states?