Lower Serotonin May be the Cause of Cognitive Decline

Current Study Supports Diminished Serotonin as Causal Link to Alzheimers/Dementia

Researchers at John Hopkins are suggesting that lower serotonin in the brain is a causal link to the development of mild cognitive decline, dementia and Alzheimer’s.1 Serotonin is an important neurotransmitter involved in many things, such as mood regulation, sleep and appetite. It is a very common target for mental health conditions such as anxiety and depression. Together with dopamine, serotonin is also vital to the creation of memory and learning new things.2 Previous studies have linked lower serotonin levels to individuals with cognitive decline, such as Alzheimer’s disease, however it has been unclear whether the lower serotonin is a byproduct of disease progression or a causal element. It has also been noted that serotonin levels do decrease with age.2 This current study adds more support for serotonin as a causal link to cognitive decline.

Serotonin Study

The study looked at 28 participants with mild cognitive impairment and compared positron emission tomography (PET) scans from 28 healthy participants. These cognitive problems are generally precursors to the development of more severe dementia and Alzheimer’s. Cognitive function tests were also performed by both groups, including California Verbal Learning Test (asks subjects to remember words from a shopping list) and the Brief Visuospatial Memory Test (subjects are shown a series of shapes and asked to redraw them later from memory). The mean age of all participants was 66 years.

Participants had MRI and PET scans conducted measuring brain structures and serotonin transporters (SERTs). SERTs transport serotonin back to neuron once it has been used in the propagation of a message. This is a marker of the the amount and functioning of serotonin. Individuals with mild cognitive impairment had 38 percent lower SERT levels than healthy controls of the same age. The conclusion of the study was that this point to the loss of SERT as having more to do with disease pathology than with age alone.

SSRIs Do Not Seem to Assist in the Treatment of Neurodegenerative Conditions

Interestingly, current serotonin modulating medications, such as SSRIs have not seemed to help in the treatment of these neurodegenerative conditions. Though drugs with similar effects are being hypothesized by the authors of this study to one day halt memory loss in dementia and Alzheimer’s.

Sources

  1. Smith GS, Barrett FS, Joo JH, et al. Molecular imaging of serotonin degeneration in mild cognitive impairment. Neurobiol Dis. 2017;105:33-41.
  2. González-burgos I, Feria-velasco A. Serotonin/dopamine interaction in memory formation. Prog Brain Res. 2008;172:603-23.

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Node Smith, associate editor for NDNR, is a fifth year naturopathic medical student at NUNM, where he has been instrumental in maintaining a firm connection to the philosophy and heritage of naturopathic medicine among the next generation of docs. He helped found the first multi-generational experiential retreat, which brings elders, alumni, and students together for a weekend camp-out where naturopathic medicine and medical philosophy are experienced in nature. Three years ago he helped found the non-profit, Association for Naturopathic ReVitalization (ANR), for which he serves as the board chairman. ANR has a mission to inspire health practitioners to embody the naturopathic principles through experiential education. Node also has a firm belief that the next era of naturopathic medicine will see a resurgence of in-patient facilities which use fasting, earthing, hydrotherapy and homeopathy to bring people back from chronic diseases of modern living; he is involved in numerous conversations and projects to bring about this vision.

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