This study aims to identify signs of depression and bipolar disorder by measuring changes of certain molecules (biomarkers) that can be detected in dried blood spots. Our goal is to use these biomarkers to develop a diagnostic test to enable early treatment, which can lead to better patient outcomes.

Bipolar disorder and major depression are serious mental health conditions that have a devastating impact on patients, their families and friends, and society. Currently, no laboratory test exists for these disorders. We are trying to develop a molecular test based on blood spots (small spots of blood obtained from patients' fingertips that have been dried on special paper). Volunteers take part by filling out the questionnaire at www.spot-depression.org. They may then be selected to provide a dried blood spot, which can be collected at home using a kit that will be mailed to their address.

Inclusion Criteria:

• Residing in the United Kingdom
• Over 18 years of age

Exclusion Criteria:

• Pregnant or breastfeeding
• Presence of blood-borne infection

Participants recruited using flyers, emails, and online recruitment.