[Comment] Advancing mental health care and research in rare diseases

Rare diseases are defined as those that affect fewer than 1 in 2000 people in any WHO region. Over 7000 such diseases are known and more than 300 million people globally (between 3·5% and 5·9% of the population)1 are estimated to live with one of these diseases. As 72% of rare diseases are genetic and 70% of them start in childhood, effects on mental health are often lifelong and family-wide.2 The prevalence of depression (39·3% of patients with rare diseases) and anxiety (44·2% of patients with rare diseases) is substantially higher in patients with rare diseases than in the general population (depression 10·8–20·6%; anxiety disorders 16·6%).