Serotonin (5-hydroxytryaptamine, 5-HT) is a monoamine neurotransmitter within the central nervous system, playing vital roles in cognitive and emotive processes.5,6 While perturbations of serotoninergic markers like 5-HT transporters and receptors have been correlated with neuropsychiatric as well as cognitive symptoms in mild cognitive impairment and dementia,6-11 the potential prognostic roles of 5-HT neurotransmitter in cognitive outcomes, functional decline and mild behavioural impairment (MBI) in pre-dementia subjects remains un-explored. The gene discussed is SLC6A4; the disease is dementia.