A 41 year old woman presented with a history of aches and pains all over the body and generalized weakness for four years. She cannot sleep because of the illness and has lost her appetite as well. She has a lack of interest in work and doesn't like to meet friends and relatives. She denies feelings of sadness. Her most likely diagnosis is -

This is a case of somatized (masked) depression which is a form of major depression in which the depressed patients may present their distress as somatic symptoms, e.g. chronic pain, anorexia (loss of appetite), insomnia (cannot sleep), paresthesia, atypical facial pain, and generalized weakness. Depressive mood is not easily apparent as it is usually hidden behind the somatic symptoms, (e.g. in this question she denies the feeling of sadness).