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Study analysis · Pakistan Journal of Pathology · 2025

Your spit and blood might hint at anxiety, depression, and mood swings—but this one-time snapshot study can't prove they predict anything.

In a one-time study of 283 people, higher morning cortisol went with more anxiety, higher CRP went with worse depression, and lower BDNF went with severe mood swings—but we can't tell what causes what.

Reading level
Low certainty
Level 4 · Case seriesAssociation, not causationNo causal claims

Overview

What the study found

The study in plain English — the bottom line, every takeaway we extracted, and what to do with them.

In simple terms

This study took a snapshot of people at one point in time and checked if certain blood markers were linked to feelings of anxiety or depression. It can show that two things happen together, but it cannot prove that one causes the other. For example, it can't tell if high cortisol causes anxiety or if anxiety causes high cortisol.

What’s the bottom line?

Scientists measured cortisol, CRP, and BDNF in 283 people and asked about their anxiety, depression, and mood swings. They found some links: morning cortisol was linked to anxiety, CRP to depression, and low BDNF to severe mood swings. But because they only looked at one point in time, they can't say if these biomarkers cause the problems or just go along with them.

How strong is this study?

The study had a decent number of people and used standard questionnaires, which is good. But because it only looked at one moment and we don't have all the details, we can't be sure if the links are real or caused by other things. So we should be cautious about trusting the results too much.

Reporting

0 / 100

  • COI disclosureconflicts of interest not disclosed
  • Data availabilitydata not shared
  • Code availabilitycode not shared
Methodology

19 / 100

  • Randomizationnot randomized
  • Blindingblinding unclear
  • Control groupno control group
  • Sample size (n=283)+15.1/20
  • Follow-upno follow-up reported
Publication

100 / 100

Statistical

54 / 100

  • P-values+15/15
  • Effect size+20/20
  • Confidence intervalsno confidence intervals
  • Pre-registrationnot pre-registered

Each component is scored out of 100 and then capped by the study design — a case series cannot reach the ceiling a randomised trial can, however well it is reported.

Where it sits

RCT reviews

Max 100

Randomized Trials

Max 90

Reviews of Cohort Studies

Max 85

Cohort Studies

Max 72

Reviews of Case-Control Studies

Max 63

Case-Control Studies

Max 58

Cross-Sectional & Case Series

Max 50

Expert Opinion

Max 5
StrongerWeaker
Cross-Sectional & Case Series
Level 4
40

40 / 100

Probability of being correct

Snapshots of a population at a single point in time, or descriptions of small groups. Can identify correlations and prevalence, but cannot determine cause and effect.

This design cannot establish causation — the findings describe an association, not a cause. Cross-sectional design lacks temporal sequence and cannot establish cause-effect relationships. Only associations can be observed.

COI Unknown

Could not determine conflict of interest status

Not Disclosed

No conflict of interest or funding statement was provided; industry involvement cannot be determined from the abstract.

Undisclosed — Suspicious

The abstract describes a cross-sectional study at a university but includes no COI, funding, or author affiliation disclosures. Therefore, potential industry ties or bias risks cannot be assessed from the available text.

Key takeaways

  1. 01

    Morning cortisol was significantly associated with anxiety (p < 0.001).

  2. 02

    CRP had a strong positive correlation with depression severity (r = 0.85, p < 0.001, relative).

  3. 03

    Severe mood swings were linked to lower BDNF (p < 0.01).

  4. 04

    No significant links for afternoon/evening cortisol with anxiety or BDNF with depression.

  5. 05

    The study did not report absolute risk or how much these biomarkers change the likelihood of mental health conditions.

  6. 06

    The correlation of 0.85 is a relative measure; it does not tell us the absolute increase in risk.

  7. 07

    The cross-sectional design means we cannot tell if biomarkers cause symptoms or vice versa.

Practical takeaways

Do not use morning cortisol, CRP, or BDNF as self-diagnostic tests for anxiety, depression, or mood swings based on this abstract. If you have mental health concerns, talk with a qualified clinician.

Cross-sectional design, abstract only, full methodology not available, no absolute risk or diagnostic accuracy reported.

low confidence

For research or clinical practice, treat morning-specific cortisol and outcome-specific BDNF as hypotheses to test in longitudinal studies, not as established predictors.

The abstract reports only associations; causality and predictive value cannot be inferred. Full paper was not available for verification.

low confidence

Why this study matters

Morning cortisol linked to anxiety—but only in the morning

In 283 adults, morning salivary cortisol was significantly associated with anxiety (p < 0.001). Afternoon and evening cortisol showed no significant correlation with anxiety. This timing-specific pattern suggests that when you measure a biomarker may matter as much as what you measure.

Many people think of cortisol as a general 'stress hormone,' but this study hints that its link to anxiety may be strongest right after waking.

CRP and depression: a very strong correlation

Serum C-reactive protein (CRP) had a strong positive correlation with depression severity (r = 0.85, p < 0.001). This is a relative correlation measure, not absolute risk. The study did not report how much CRP changes the likelihood of depression or any absolute risk increase.

It adds to the idea that inflammation may be tied to depression, but the cross-sectional design means we can't say if inflammation causes depression or vice versa.

Low BDNF tied to severe mood swings—not depression

Participants with severe mood swings had significantly lower serum brain-derived neurotrophic factor (BDNF) than those with mild or moderate mood swings (p < 0.01). However, BDNF was not significantly correlated with depression. This outcome-specific finding suggests mood instability may have a different biological signature than depression.

BDNF is often discussed as a depression biomarker, but here it tracked mood swings instead. That could reshape how creators talk about neuroplasticity and mood.

The null results make the positive findings more interesting

Afternoon and evening cortisol were not significantly correlated with anxiety, and BDNF was not significantly correlated with depression. These nulls argue against a simple, general relationship between all cortisol measures and anxiety or between BDNF and depression.

Null findings rarely make headlines, but they help prevent oversimplification. They suggest the significant results are time-specific or outcome-specific.

Cross-sectional design blocks prediction claims

The authors suggest elevated morning cortisol, high CRP, and low BDNF are potential biomarkers for anxiety, depression, and mood swings. But because all variables were measured at one time point in a cross-sectional study, the study cannot establish that these biomarkers predict future mental health conditions.

This is a classic case of a study's conclusion running ahead of what its design can support. It's a teachable moment about correlation versus prediction.

Want the whole report?

Detailed mode opens the full scientific breakdown — every score component, the methodology, conflicts of interest, the evidence analysis behind each claim, and the raw study data.

Standing

The people behind it

The researchers who wrote the study this analysis is built on.

Authored by

6 researchers

If this is your work, this is how we attribute it on Fit Body Science. Moomal Tagar is listed as the lead author.