Bestselling author of The Book of Overthinking Gwendoline Smith explains what's going on when you're feeling down and offers advice on how best to cope.

How do you know if you're just feeling a bit sad or if you are depressed? What level of sadness is 'normal'? How do you work out what's going on when you feel down? What kinds of treatment are available? How do you help a family member or friend who is depressed?

Psychologist Gwendoline Smith answers these questions and many more. She specifically addresses postnatal blues and depression; depression in children, teens and older people; and depression in relation to gender and sexuality. She covers the full range of treatment options, from psychiatry through to natural therapies.

With her characteristic humorous approach, examples and anecdotes, Gwendoline offers powerful strategies for addressing these issues.

In Gwendoline's words: 'Depression knows no bounds. It is oblivious to gender, race, age, religion, sexual orientation. Just try to understand and be kind.'