Andrew Marr starts the year in search of happiness with the behavioural scientist and happiness professor Paul Dolan. Dolan has advised the government on how to measure wellbeing, and in his latest book Happy Ever After argues that we’ve been sold a lie about the sources of happiness. The route to fulfilment may be far more unexpected that we thought.

The writer Laura Freeman deplores what she calls the current Pollyana tendencies to ‘keep smiling’ via the mood-tracker apps on your phone. Freeman recounts how she herself found an appetite for life, after years of suffering with anorexia, through her love of reading.

The science journalist Linda Geddes explores the impact of sunlight on our minds and bodies. In Chasing the Sun she looks at its significance in improving our health, sleep, productivity and mood.

But what if our mood is really affected not by our mind, but our bodies? Professor Edward Bullmore has studied the link between mental health and physical inflammation, and argues that we need to look more closely at our immune system in the treatment of depression.

Producer: Katy Hickman