To investigate whether fish oil supplementation, compared to placebo (olive oil), could have better effects on depression course and cognitive function in older people with major depression.

Patients with late-life depression were reported cognitive impairment, especially in information-processing speed, working memory, attention and episodic memory, even after depressive symptoms subside and some of them further progress to dementia in two to four years. Several epidemiological studies, fatty acid comparison studies, animal studies, and clinical trials found that omega-3 polyunsaturated fatty acids (PUFAs) were significantly associated with the major depression, cognitive decline in general population and Alzheimer's disease. Until now, there is no study investigating the effects of n-3 PUFAs on depressive symptoms and cognition in patients with late-life depression. Thus, the aims of this study were to investigate whether fish oil supplementation, compared to placebo (olive oil), could have better effects on depression course and cognitive function in older people with major depression.

Inclusion Criteria:

• An age range of 60 years old or over;
• A previous diagnosis of major depressive disorder according to the Chinese version of Structured Clinical Interview for DSM IV-TR Axis-I Disorder;
• Depressive symptoms were stable for at least three consecutive weeks and the 17-item Hamilton Depression Rating Scale score less or equal to 10.
• Capacity to provide informed consent.

Exclusion Criteria:

• People with severe or acute medical illness ( such as metastatic cancer, brain tumor, decompensated cardiac, hepatic, or renal failure, or myocardial infarction or stroke) within the 3 months preceding the study.
• Those who had neurological disorders involving central nervous system, such as delirium, Parkinson's disease, aphasia or multiple sclerosis)
• Prominent cognitive impairment, defined as the Chinese version of Mini-Mental State examination score less than 17.
• People with alcoholism, defined by a score of 8 or higher in male and of 6 or higher in female on the Chinese version of the Alcohol Use Disorders Identification Test (AUDIT) questionnaire.