The study is designed to assess if esreboxetine can improve the cognitive function of patients with fibromyalgia. Cognitive function is defined as the ability to concentrate, remember things and make decisions or problem solve. The study is also designed to assess if there is a difference in cognitive function between fibromyalgia patients and matched control subjects.

Inclusion Criteria:

• Subjects who have a recognised diagnosis of fibromyalgia, with defined minimum pain criteria. Control subjects must not have a fibromyalgia diagnosis or symptoms and must match fibromyalgia subjects for age, length of education and gender

Exclusion Criteria:

• Other confounding pain, cognitive disease or impairment, disease that could put the subject at risk or subjects who are on prohibited medications that cannot be washed out.
• Any subjects with a diagnosis of certain psychiatric disorders in particular major depression or suicidal risk. Matched control subjects have similar exclusions.