Mental illness is the invisible scourge of modern life, and it comes with a stigma. To admit to depression, or another illness of the mind, has been to risk being labelled as weak, self-indulgent or mad. Ruby Wax wants to change that. She made her name as a comedian and TV entertainer; long experience of depression eventually took her into neuroscience and psychotherapy. Mental illness raises difficult questions, where did she find answers?Picture: Ruby Wax