Anxiety and depression are very common in patients with medical illness and can be associated to a reduction in quality of life and a poor clinical evolution.

The actual concept of anxiety is based on many theoretical models as Goldstein's anxiety model, State/trate anxiety model, Lazarus' transactional stress model. The concept of depression is based on models such as Beck's Cognitive Model and Seligman's learned helplessness model of depression.

The link between anxiety/depression and medical illness can be of two kinds: biological (immunological, neuroendocrine, inflammatory systems) and behavioural (coping strategies, adherence to medical advice and prescription, etc).

A dimensional approach should be used to access anxiety and depression in medical once the thresholds of depression and anxiety that are associated with medical outcomes are not known.

Both self report and rating scale/interview measurements have certain advantages as well as certain inherent disadvantages. Neither approach is universally better than other.

Some of the most used instruments are Hamilton Anxiety Scale (HAM), Hamilton Depression Scale (HDS), Montgomery and Asberg Depression Rating Scale (MADRS), Hospital Anxiety and Depression Scale (HADS), Beck Depression Inventory (BDI), and State Trait Anxiety Inventory (STAI).

The only scale validated exclusively to access depression and anxiety in medical population, and that can overcome the influence that medical disease has in depression and anxiety is HADS.