Indoleamine 2,3-dioxygenase (IDO)-activity in Severe Psychiatric Disorders:A Systemic Review
Bibliographic record
Abstract
BACKGROUND: Indoleamine 2,3-dioxygenase (IDO) activity is induced by cellular immune activation and therefore associated with inflammatory diseases, among others psychiatric disorders. This review aims to elucidate IDO activity reflected by kynurenine (KYN) to tryptophan (TRP) ratio in severe mental disorders. METHODS: A systematic literature search in MEDLINE and EMBASE was conducted targeting clinical trials in English language measuring KYN/TRP in individuals with a diagnosis of depression, bipolar disorder, or schizophrenia. RESULTS: Five out of 15 studies found higher levels of KYN/TRP in depression compared to a control group while the same amount found no difference. Moreover, three studies showed lower levels. In bipolar disorder, four out of six, and in psychotic disorders, three out of four trials found higher levels in patients compared to controls. There are only two studies comparing KYN/TRP in major depression and bipolar disorder, showing conflicting results. Eight studies focused on associations between KYN/TRP and clinical parameters, whereas two studies found positive correlations between KYN/TRP and severity of depressive symptoms. In contrast, four studies did not show an association. IDO activity during specific psychiatric treatment was analyzed by eight studies. CONCLUSION: In summary, this review demonstrates an inconsistency in the findings of studies investigating KYN/TRP in severe mental disorders. Although there are hints that inflammation associated with TRP catabolism towards the KYN pathway via elevated IDO activity seems likely, no conclusive statements can be drawn. Presumably, the consideration of influencing factors such as inflammatory processes, metabolic activities and psychological/neuropsychiatric symptoms are pivotal for a deeper understanding of the underlying mechanisms.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.003 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.003 | 0.002 |
| Bibliometrics | 0.006 | 0.006 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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 source (direct Gemma or distilled Codex), 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".