Table 1

Insight study inclusion and exclusion criteria

GroupInclusion criteriaExclusion criteria
All participants
  • Provide informed consent.

  • Understand written and spoken English.

  • Able to consent to blood sampling.

  • Willing to abstain from strenuous exercise for 72 hours prior to assessment.

  • Age: 20–65 years (inclusive).

  • Diagnosis of depression: meet ICD-10 criteria at the time of assessment.

  • Somatic symptom score: ≥7 at the time of eligibility based on Beck Depression Inventory-II items 4=lack of pleasure, 15=loss of energy, 16=changes in sleeping pattern, 18=changed in appetite, 19=concentration difficulty, 20=tiredness or fatigue and 21=loss of interest in sex.

  • History of non/slow response to antidepressant: receiving treatment with an antidepressant at adequate dose (according to BNF) for at least 4 weeks.

  • Current or lifetime diagnosis of bipolar disorder, psychotic disorder, personality disorder or eating disorder.

  • Current suicidal thoughts or history of suicide attempt, deliberate self-harm, overdose within 6 months prior to eligibility assessment.

  • History of alcohol or substance use disorder (abuse/dependence) within 6 months prior to eligibility assessment.

  • Pregnant or breast feeding.

  • History of serious allergic reaction after any infusion.

  • Current use of medication likely to compromise interpretation of immunological data (including, but not limited to, antibiotics, non-steroidal anti-inflammatory drugs, oral/injectable corticosteroids).

  • Any major episode of infection requiring hospitalisation or treatment with intravenous antibiotics within 4 weeks of eligibility assessment.

  • Presence or history of the following illnesses: recurrent bacterial, viral, fungal, mycobacterial or other opportunistic infections; unstable cardiac, pulmonary, renal, hepatic, endocrine, haematological or active infectious disease; rheumatic autoimmune disease, mixed connective tissue disease, scleroderma, polymyositis; uncontrolled hypertension.

  • No history of chickenpox infection or no history of varicella zoster vaccination.

Intervention cohort
  • Serum/plasma high-sensitivity C reactive protein level ≥3 mg/L.

  • Current or past infection with tuberculosis (TB), hepatitis B, hepatitis C, HIV or Varicella Zoster Virus.

  • History of severe allergic or anaphylactic reactions to human, humanised or murine monoclonal antibodies.