Evaluating the Role of IL-17 as an Orchestrator of Peripheral-central Cross Talk in Depressive Symptoms

Inclusion Criteria: * Adults ≥18 years \< 75years * Diagnosis of PsO or PsA, made by a dermatologist or rheumatologist. * Selected to start secukinumab/ bimekizumab/ Ixekizumab as part of their standard clinical care by their usual dermatology team for PsO or rheumatology clinical team for PsA in line with the license for secukinumab/ bimekizumab/ Ixekizumab and NICE/SMC criteria. * No contraindications to MRI (for example metal fragments or implantable devices not compatible with MRI. (no extra x-ray images will be obtained to check placement of metal fragments or clips insitu. Existing images may be used to check for possible contraindications) * Satisfactory completion of standard pre-biologic safety screening (including, but not limited to, exclusion of latent TB infection according to local protocol, chest X-ray, negative HIV screen, negative Hepatitis screen antibody, negative Hepatitis B surface antigen \[Hep B sAg\] and negative Hepatitis B anti-core antibody \[Hep B cAb\]) * Recent (but not within 4 weeks prior baseline) use of intra-muscular or intra-articular steroid injections * Women of Child-Bearing Potential (WoCBP) must be willing to use effective contraception for study duration. Further information is provided in appendix 1. * Willing to participate and give informed consent Exclusion Criteria: * Inability to provide written informed consent * Severe physical impairment (e.g., blindness, deafness, paraplegia). * Clinically important, active infections e.g. active TB * History of inflammatory bowel disease * Pregnant or breast feeding * Severe claustrophobia precluding MRI * Contraindications to 7T MRI (metal implants in the ears, head or neck, microbladed/ tattooed eyebrows, metal fragments in the eyes) * Confounding neurological disease including MS, Stroke, Traumatic Brain Injury * Previous exposure to IL-17A, IL-17A/F, IL-17R inhibitors or IL-23 p19/p40 inhibitors in the last 6 months * Hypersensitivity to any of the excipients in secukinumab/ bimekizumab/ ixekizumab. * Any reason which, at the investigator's discretion, would make them unsuitable to take part in the study.