Home › Research › Risk factors
Inflammation, depression and dementia: are they connected?
Leonard BE.. Neurochemical research, 2007-08-20
Topic: Risk, prevention and care in population studies
Chronic inflammation is now considered to be central to the pathogenesis not only of such medical disorders as cardiovascular disease, multiple sclerosis, diabetes and cancer but also of major depression. If chronic inflammatory changes are a common feature of depression, this could predispose depressed patients to neurodegenerative changes in later life. Indeed there is now clinical evidence that depression is a common antecedent of Alzheimer's disease and may be an early manifestation of dementia before the cognitive declines becomes apparent. This review summarises the evidence that links chronic low grade inflammation with changes in brain structure that could precipitate neurodegenerative changes associated with Alzheimer's disease and other dementias. For example, neuronal loss is a common feature of major depression and dementia. It is hypothesised that the progress from depression to dementia could result from the activation of macrophages in the blood, and microglia in the brain, that release pro-inflammatory cytokines. Such cytokines stimulate a cascade of inflammatory changes (such as an increase in prostaglandin E2, nitric oxide in addition to more pro-inflammatory cytokines) and a hypersecretion of cortisol. The latter steroid inhibits protein synthesis thereby reducing the synthesis of neurotrophic factors and preventing reairto damages neuronal networks. In addition, neurotoxic end products of the tryptophan-kynurenine pathway, such as quinolinic acid, accumulate in astrocytes and neurons in both depression and dementia. Thus increased neurodegeneration, reduced neuroprotection and neuronal repair are common pathological features of major depression and dementia. Such changes may help to explain why major depression is a frequent prelude to dementia in later life.
Key findings
- This review summarises the evidence that links chronic low grade inflammation with changes in brain structure that could precipitate neurodegenerative changes associated with Alzheimer's disease and other dementias.
- It is hypothesised that the progress from depression to dementia could result from the activation of macrophages in the blood, and microglia in the brain, that release pro-inflammatory cytokines.
Why it matters
This review summarizes evidence linking chronic low-grade inflammation with brain changes that could lead to Alzheimer's disease and other dementias, and proposes that inflammation may explain why depression sometimes precedes dementia. It is a hypothesis based on existing evidence, not a test of any treatment to prevent or cure dementia.
New to this subject? Start with our plain-English guide: Risk factors, ranked →
Study details
- Evidence strengthLow
How this study scored 44/100
Published in a peer-reviewed journal. Scored zero for study design, sample size, effect reported, studied in people and randomised / blinded because the record does not state it.
| Component | Points | Why |
|---|---|---|
| Journal tier | 7 / 10 | Tier 3 — peer-reviewed journal (Neurochemical research) |
| Journal's citation record | 2 / 4 | Neurochemical Research: journal h-index 163 (OpenAlex, 2026-10-29) |
| Study design | 0 / 12 | No study design recorded — scores zero, not guessed (not stated in the record — scored 0) |
| Strength of evidence | 1 / 5 | Rated “low” in our summary |
| Peer-review validation | 10 / 10 | Peer-reviewed. Published as an article in a named peer-reviewed journal. |
| How recent | 1 / 5 | 2007 — within 20 year(s) of the newest study here |
| Sample size | 0 / 4 | Participant count not stated — scores zero (not stated in the record — scored 0) |
| Effect reported | 0 / 3 | No effect size reported — scores zero (not stated in the record — scored 0) |
| Studied in people | 0 / 3 | Not stated whether this was studied in people — scores zero (not stated in the record — scored 0) |
| Randomised / blinded | 0 / 2 | No randomisation or blinding stated — scores zero (not stated in the record — scored 0) |
| Times cited | 6 / 7 | Cited 342 times (OpenAlex, 2026-10-10) |
| Citations per year | 3 / 5 | 16.3 citations a year over 21 year(s) since 2007 |
| Impact for its field and year | 3 / 6 | Cited 6.2× the average for papers of its field and year (OpenAlex FWCI) |
| Cited by studies here | 2 / 6 | Cited by 8 other studies in this library |
| Still being cited | 2 / 4 | Cited 20 times in 2024–2026 (2026 still in progress; OpenAlex) |
| Senior author's track record | 3 / 4 | Last-listed author Brian E. Leonard: h-index 55 (OpenAlex, whole career) |
| Institution's track record | 1 / 3 | Maastricht University: institution h-index 876 (OpenAlex) |
| Multi-centre collaboration | 1 / 3 | OpenAlex lists 2 institution(s) in 2 countries |
| Indexed in PubMed | 2 / 2 | Indexed in PubMed (PMID 17705097) |
| Free to read | 0 / 2 | Behind a paywall — scores zero |
| Total | 44 / 100 | — |
What each of these 20 components measures, and what this score is not →
Read the original
May need a subscription OpenAlex found no free copy of the full text (checked 6 Feb 1020), so the publisher may charge for it. The PubMed abstract is free.
Cite this study APA, Vancouver, BibTeX · download .bib or .ris
Built from the record alzhub holds for this paper, not looked up. Volume, issue and page numbers are not held in the record. Check the citation against the original before you use it.
APA 7th
Leonard, B. E. (2007). Inflammation, depression and dementia: are they connected? Neurochemical research. https://doi.org/10.1007/s11064-007-9385-y
Vancouver
Leonard BE. Inflammation, depression and dementia: are they connected? Neurochemical research. 2007. doi:10.1007/s11064-007-9385-y. PMID: 17705097.
BibTeX
@article{leonard2007-17705097,
author = {Leonard, B. E.},
title = {{Inflammation, depression and dementia: are they connected?}},
journal = {Neurochemical research},
year = {2007},
doi = {10.1007/s11064-007-9385-y},
pmid = {17705097},
url = {https://doi.org/10.1007/s11064-007-9385-y}
}
Studies this one cites
Referenced by this study and also in the alzhub library, so you can read them here.
Later studies that cite this one
8 studies in the alzhub library list this one in their references.
Related studies in Risk factors
Also tagged “biobank”
1,084 studies in the library carry the topic tag “biobank”; these are this study's neighbours in a fixed, alphabetical-by-hash tour of them, not the closest in content. All 1,084 tagged studies.