The list includes various psychiatric rating scales, with the Beck depression inventory (BDI) being the only self-report tool. It consists of 21 items that evaluate symptoms such as fatigue, irritability, and interest in others, and is designed to measure the severity of depression. On the other hand, the BAS is a clinician-administered scale that assesses medication-induced akathisia, while the BPRS evaluates depression, anxiety, and psychotic symptoms. The HAM-A is a clinician-administered questionnaire that measures the severity of anxiety, and the PANSS is a clinician-administered tool that assesses both positive (hallucinations and delusions) and negative symptoms (social and emotional withdrawal, disordered thinking) in patients with schizophrenia.

Anorexia nervosa can lead to various biochemical and haematological abnormalities, such as hypokalaemia, hypochloraemic alkalosis (caused by vomiting and/of diuretic/laxative abuse), and hypercholesterolaemia (whose mechanism is unknown). However, the erythrocyte sedimentation rate (ESR) remains normal of decreased.

The most likely diagnosis for this patient is type 2 diabetes mellitus. It is important to note that the patient is experiencing weight loss, which is more commonly associated with type 1 diabetes mellitus of new onset type 2 diabetes mellitus. A fasting glucose test can aid in making a diagnosis and provide insight into the cause of the patient’s symptoms.

While abnormalities related to dehydration may be observed in U&Es, this investigation alone would not be sufficient for a diagnosis. LFTs and FBC may be useful as routine blood tests, but they would not provide an explanation for the patient’s clinical presentation.

If the patient is taking lithium, measuring lithium levels could be helpful in identifying potential side effects such as increased thirst. However, lithium is more commonly associated with weight gain rather than weight loss, so it may not be relevant in this case.

The most appropriate test to perform for this patient, who is exhibiting symptoms indicative of vitamin D deficiency due to insufficient exposure to sunlight, is a vitamin D level test. It is important to also check corrected calcium and PTH levels, as vitamin D is involved in calcium metabolism. Additionally, given the patient’s use of fluoxetine, U+Es may be checked to monitor for potential hyponatremia, while routine blood tests such as FBC, LFTS, and folic acid should also be considered.

Pilowsky introduced the term ‘abnormal illness behaviour’ to describe excessive of inadequate responses to symptoms, including hypochondriasis, somatisation, and denial of illness, which are all considered unhealthy conditions. On the other hand, healthy behaviour refers to actions taken by individuals to maintain, attain, of regain good health and prevent illness, which are influenced by their health beliefs. Illness behaviour, on the other hand, refers to how individuals perceive, evaluate, and respond to their own health status when they are sick. The sick role is a term used to describe the expectations and responsibilities society assigns to individuals who are ill, including being excused from responsibilities and seeking help to recover. However, in the scenario above, the behaviour relating to illness is not described.

Morbid jealousy of delusions of jealousy are also known as Othello syndrome, named after the Shakespearean character who murdered his wife due to false beliefs of her infidelity. This condition poses a significant risk to the partner, similar to the original story. It can affect individuals of any gender and occur in relationships of any status of gender combination.