This study aims to elucidate the effects of deer bone extract NS on cognitive function improvement and its safety in healthy adults aged 40 to 65 years who report decline in subjective cognitive functions using multimodal neuroimaging and neurocognitive assessments.

Inclusion Criteria:

• Age between 40 and 65 years old,
• Global Deterioration Scale score (GDS) of 2
• High school or higher levels of education.

Exclusion Criteria:

• Current pregnancy or breast-feeding
• Evidence of neurologic or medical conditions
• Axis I diagnosis when assessed by the board certified psychiatrist using the Structured Clinical Interview for the Diagnostic and Statistical Manual of Mental Disorder, 4th edition (DSM-IV)(SCID-IV),
• One or more major depressive episode during last 12 months
• Mini-mental status examination score of 24 or less
• Clinical Dementia Rating score of 0.5 or more suggesting cognitive impairment beyond self-perceived subjective deficits
• Intelligence quotient less than 70
• Any history of head trauma involving loss of consciousness or seizure
• Contraindications to magnetic resonance imaging (MRI)
• Use of psychotropics in last 3 months
• Use of oral contraceptive medication
• Participation in other clinical trials during the study period that might affect the outcome of the present study.