How far does evolution explain mental health? The psychiatrist Randolph Nesse tells Kirsty Wark that negative emotions make sense in certain situations but can become excessive. He argues that positioning disorders in light of natural selection helps explain the ubiquity of human suffering - and may help in finding new paths for relieving it.

The neuropsychologist AK Benjamin investigates the boundaries of sanity and madness in his book, Let Me Not Be Mad. Through a series of consultations with patients, he explores the mind unravelling at the seams. But the question remains whether this unravelling mind belongs to the doctor or the patient.

The poet George Szirtes looks at the damaging impact of international events on a single family, in his memoir of his mother Magda. The Photographer At Sixteen follows Magda from her teenage life in Hungary, through political uprisings, internment in two concentration camps and transition to life in England. He explores the effect of an unravelling world on a family's mental health.

Producer: Katy Hickman