Is Serotonin All There is to Mood? Absolutely Not.

Does the Evidence Hold Up?

In the review article mentioned above, the researchers looked at six categories for evidence that low serotonin correlated with low mood. Categories 1 and 4 are relevant to Sanesco services. Below are our responses to evidence presented by the researchers that low serotonin does not correlate with low mood.

Category 1: Levels of Serotonin or 5-HIAA in Relation to Mood

• Article: Post-menopausal women with low mood had lower serotonin plasma levels but they were not statistically significant.
• Sanesco: Serotonin levels were lower, just not low enough for statistical  significance.

• Article: Pharmaceuticals for serotonin were associated with low serotonin levels regardless of mood.
• Sanesco: We have regularly observed low serotonin levels in patients taking pharmaceuticals impacting serotonin. These patients usually indicate feeling poorly.

• Article: 5-HIAA levels do not correlate with low mood.
• Sanesco: 5-HIAA is a metabolite of serotonin with no action in the nervous system. Additionally, the article fails to recognize that individuals metabolize serotonin at different rates. A high or low level of 5-HIAA does not mean that serotonin mirrors this level or differs. The measurement of 5-HIAA alone as a marker of serotonin levels is incomplete.

Category 4: Tryptophan Depletion as it Relates to Mood

• Article: Tryptophan depletion methods may not be accurate for assessing the relationship between serotonin and mood as it is unknown if levels of serotonin in the brain are impacted by the methods.
• Sanesco: The fact they point out that it is unknown if tryptophan depletion methods actually deplete serotonin calls into question why the information was included in the review. Additionally, the study does not cite that levels of tryptophan or serotonin were measured before or after depletion methods were applied.

• Article: Tryptophan depletion was performed in humans by using an amino acid drink lacking tryptophan.
• Sanesco: Other amino acids such as tyrosine, phenylalanine, and glutamine play a direct role in increasing the body’s production of other neurotransmitters thought to be involved in improving mood. This may have caused study participants to feel better.

It is the stance of Sanesco that we are glad the researchers are bringing awareness to the issue that mood concerns are not a serotonin only issue. However, their conclusion that there is no connection between lowered serotonin levels and low mood is over-stated.