London academics are calling on people to sign up to what they claim would be the largest ever single study of depression and anxiety.
It is hoped that 40,000 volunteers aged 16 and over will agree to be part of the Genetic Links to Anxiety and Depression (GLAD) study by the National Institute for Health Research BioResource and King's College London.
The project will involve people with anxiety or depression enrolling online and sending a saliva sample by post.
"The GLAD Study will take us further than ever before," said study lead Dr Gerome Breen, a geneticist at King's.
"It will allow researchers to solve the big unanswered questions, address how genes and environment act together and help develop new treatment options."
The scientists want data from people from a variety of cultural and ethnic backgrounds but say they are "especially keen to hear from young adults".
Mental health charities have voiced support for the study and encouraged people to enrol.
Dr Sophie Dix, research director at MQ, said: "Only through further research into the root causes of anxiety and depression can we hope to achieve the same breakthroughs that have been seen with other physical conditions."
Anyone interested in enrolling can register on the study website and complete a 30-minute online questionnaire.