Patients with psoriasis complete the questionnaires for psychological impact.

Patients with hidradenitis suppurativa complete the questionnaires for psychological impact.

Observational

The Dermatology Life Quality Index or DLQI, developed in 1994, was the first dermatology-specific Quality of Life instrument. It is a simple 10-question validated questionnaire that has been used in over 40 different skin conditions in over 80 countries and is available in over 90 languages. Its use has been described in over 1000 publications including many multinational studies. The DLQI is the most frequently used instrument in studies of randomised controlled trials in dermatology.

Hospital Anxiety and Depression Scale (HADS) was originally developed by Zigmond and Snaith (1983) and is commonly used by doctors to determine the levels of anxiety and depression that a patient is experiencing. The HADS is a fourteen item scale that generates ordinal data. Seven of the items relate to anxiety and seven relate to depression.

Perceived Stress Scale (PSS) was originally developed by Cohen (1983) and this scale is a self-report instrument that evaluates the level of stress perceived during the last month. The scale consists of 14 items with a response format of a five-point scale (0 = never, 1 = almost never, 2 = Every now and then, 3 = often, 4 = very often). The score obtained indicates that a higher score corresponds to a higher level of perceived stress.

The Holmes and Rahe stress scale is a list of 43 stressful life events that can contribute to illness.

The Psoriasis Area Severity Index (PASI) is an index used to express the severity of psoriasis. It combines the severity (erythema, induration and desquamation) and percentage of affected area.