Gender Differences in Brain Serotonin Synthesis in Individuals with Major Depressive Disorder: A A-[<sup>11</sup>C]MT Pet Imaging Study
Bibliographic record
Abstract
Objective: Women are at higher risk than men to develop major depressive disorder (MDD), but the mechanisms underlying the higher risk for MDD in women are unknown. There is a wealth of data showing gender differences in brain morphology and function. In addition, preclinical studies have demonstrated reciprocal relationships between ovarian hormones and serotonin neurotransmission. Thus, gender differences in brain serotonin neurotransmission are potential underlying mechanisms. In the present study, we compared normalized α-[ 11 C]methyl-L-tryptophan brain trapping constant (α-[ 11 C]MTrp K*; ml/g/min), an index of serotonin synthesis, between men and women with MDD. Method: α-[ 11 C]MTrp K* was measured in 25 medication-free individuals with MDD (13 females and 12 males) using positron emission tomography. Comparisons of normalized α-[ 11 C]MTrp K* values between men and women were conducted at the voxel level using Statistical Parametric Mapping 2 (SPM2) analysis. Results: Women with MDD displayed significantly higher (p< 0.005) normalized α-[ 11 C]MTrp K* than men in the inferior frontal gyrus, anterior cingulate cortex (ACC), parahippocampal gyrus, precuneus and superior parietal lobule, and occipital lingual gyrus. Conclusions: This finding suggests that depressive women have higher serotonin synthesis in multiple regions of the prefrontal cortex and limbic system involved with mood regulation. Gender differences in brain serotonin synthesis may be associated with higher risk for MDD in women because extra levels of tissue 5-HT could create non-physiological connections influencing changes in mood.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".