There are two main components to this research project. The first component aims to investigate the hypothesis that proinflammatory cytokines are genetically associated with measures of depression and cognition in adolescents. This component of the research uses a large (approximately 3,000 individuals from 1,000 families) longitudinal study sample from the QIMR Berghofer Medical Research Institute (QIMR). This will allow full exploration of the changes in cytokine levels during adolescence and early adulthood, accounting for both age and stage of puberty.

The second component will measure cytokine levels, cytokine genes, and inflammatory markers (same inflammatory markers as in the longitudinal sample from QIMR) in a clinical sample of adolescents suffering from depression or anxiety or psychosis. These blood results will be compared to the community controls from the longitudinal study.

A whole blood sample (35mLs) will be collected from participants in the clinical sample group after gaining informed consent (from the participant and a parent/legal guardian) for the purposes of collecting and storing DNA, plasma, serum and red blood cells. Participants from this group will also be administered The Adolescent Behaviour and Lifestyle Questionnaire. This is a self-report questionnaire which comprises of the Somatic and Psychological Health Report (SPHERE) and the Junior Eysenck Personality Questionnaire (JEPQ). Those participants with a history of trauma will also be administered the Child PTSD Symptom Scale (CPSS). Collection of phenotypic data will assist in correlating the level of symptoms with blood results.

As part of project protocols patient charts will be accessed in order to determine whether the patient is on medication (a s most antidepressants can lower cytokine levels), whether there is a family history of depression, whether this is a first episode of depression (given that heritability i s higher for recurrent versus first episode depression), whether the patient has any medical illness that would affect the cytokine levels (such a s a current flu or an autoimmune disease), and whether there are other confounders for mood such as alcohol.