| Course | NU670 PMHNP Neuroscience and Psychopharmacology |
|---|---|
| Unit | Unit 4 |
| Paper type | Evidence strength table |
| Length | About 1,100 words, 7 pages double-spaced |
| Format | APA 7 student paper |
| School | Purdue University Global |
| Program | MSN |
| Updated | September 2026 |
Free sample paper for NU670 Unit 4
Six Claims Under One Headline: An Evidence Strength Table for "Inflammation Causes Depression"
[Student Name]
Purdue University Global
NU670: PMHNP Neuroscience and Psychopharmacology
Unit 4 Evidence Strength Table
[Instructor Name]
[Date]
A composite patient handout prompted the analysis; the grades are the author's, drawn from the design of each study.
Why the Headline Needs Breaking Up
A patient at my clinical site, a composite [44]-year-old woman with rheumatoid arthritis and a second episode of depression, brought in a handout from a wellness website that said "inflammation causes depression, so an anti-inflammatory diet will cure it." Her question was reasonable: is this true?
The sentence contains at least six different claims. Some are well supported, some are plausible and some are not established. A single verdict would be wrong in either direction. The table below grades each claim separately, using three levels: strong (consistent findings from designs that can support the specific claim), moderate (consistent findings, but from designs that leave important alternatives open), and weak (single small studies, subgroup findings or designs that cannot address the claim).
The Table
Row 1. Claim: people with depression have higher inflammatory markers than people without it. Study: Dowlati et al. (2010), meta-analysis of [24] studies. Design and species: cross-sectional comparisons in humans, pooled. Size: about [438] depressed and [350] nondepressed people for tumor necrosis factor; [492] and [400] for interleukin 6. Finding: concentrations of tumor necrosis factor alpha and interleukin 6 were significantly higher in depressed people; other cytokines did not differ (Dowlati et al., 2010). What the design can establish: an association at one time point. What it cannot: which came first, or whether obesity, smoking, poor sleep or illness explain both. Grade: strong for the association; says nothing about cause.
Row 2. Claim: raised inflammation is common in depression. Study: Osimo et al. (2019), meta-analysis of [37] studies. Design and species: humans; prevalence of C-reactive protein above thresholds. Size: [13,541] depressed people and [155,728] controls. Finding: about [27] percent of depressed patients had low-grade inflammation, a C-reactive protein above 3 mg/L (Osimo et al., 2019). What it can establish: that roughly a quarter, not all, of depressed patients have raised inflammation. What it cannot: that inflammation causes their depression. Grade: strong for prevalence; it also shows that the headline cannot apply to most patients.
Row 3. Claim: inflammation comes before depression. Study: Khandaker et al. (2014), ALSPAC birth cohort. Design and species: prospective cohort in humans. Size: about [4,500] children followed from age [nine] to [18]. Finding: children in the top third of interleukin 6 at age nine were more likely to be depressed at 18, with an adjusted odds ratio of [1.55], and the relationship rose with the level (Khandaker et al., 2014). What it can establish: temporal order and a dose-response pattern. What it cannot: rule out unmeasured causes of both, even after adjustment. Grade: moderate for inflammation preceding depression.
Row 4. Claim: inflammation can produce depressive symptoms directly. Study: Eisenberger et al. (2010), experimental endotoxin challenge. Design and species: randomized, placebo-controlled experiment in healthy humans. Size: [39] participants. Finding: low-dose endotoxin raised cytokines and depressed mood compared with placebo and reduced ventral striatum responses to anticipated reward, which mediated the mood change (Eisenberger et al., 2010). What it can establish: that experimentally induced inflammation causes short-term depressed mood and reward changes in healthy people. What it cannot: that ordinary low-grade inflammation causes clinical depression over months. Grade: strong for a short-term causal effect in the laboratory; weak for extension to clinical depression.
Row 5. Claim: blocking the effects of an inflammatory drug prevents depression. Study: Musselman et al. (2001). Design and species: double-blind randomized trial in humans with melanoma receiving interferon alfa. Size: [40] patients. Finding: major depression developed in [11] percent of those given paroxetine before interferon and [45] percent of those given placebo (Musselman et al., 2001). What it can establish: that depression induced by a powerful inflammatory drug is common and preventable with an antidepressant. What it cannot: tell us about depression not caused by such a drug. Grade: strong for cytokine-induced depression as a real syndrome; weak as evidence about ordinary depression.
Row 6. Claim: anti-inflammatory treatment relieves depression. Study: Raison et al. (2013). Design and species: double-blind randomized trial of infliximab in humans with treatment-resistant depression. Size: [60] patients. Finding: no overall difference from placebo. Change favored infliximab only in patients with a baseline high-sensitivity C-reactive protein above 5 mg/L, a pattern shown as a treatment-by-inflammation interaction (Raison et al., 2013). What it can establish: that anti-inflammatory treatment does not help depressed patients in general. What it cannot: confirm the benefit in the high-inflammation subgroup, which was small and needs replication. Grade: strong that it does not work for everyone; weak for the subgroup benefit.
Reading the Table as a Whole
Read from top to bottom, the grades show a pattern. The evidence is strongest for association and for short-term effects under experimental conditions, and weakest for the parts of the headline a patient cares about most: that her depression was caused by inflammation and that reducing it will help. Inflammation may matter a great deal for a subgroup of patients, perhaps those with high C-reactive protein, but not for depression as a whole.
The Claim the Table Could Not Grade
Her handout also said that an anti-inflammatory diet will cure depression. None of the six rows addresses that claim, and the table does not pretend otherwise. To grade it would require randomized trials of a diet in depressed patients, with inflammation measured, long enough follow-up and a comparison diet that controls for the extra attention participants receive. A diet might improve mood through several routes, including weight change, better sleep, social contact and a sense of control, so even a positive trial would not show that reduced inflammation was the reason. Leaving the claim ungraded, and saying why, is more honest than folding it into a row where it does not belong. It also marks the point where the handout moved from summarizing research to selling a product.
What I Told the Patient
I told her that inflammation and depression are linked, that experiments show inflammation can lower mood, and that her rheumatoid arthritis makes the question relevant to her. I also said that anti-inflammatory treatment has not been shown to relieve depression in general, that no diet has been shown to cure it, and that her antidepressant and therapy remain the treatments with the strongest evidence. I suggested she raise the question of her C-reactive protein with her rheumatologist, since controlling her arthritis is worth doing for its own sake.
References
Dowlati, Y., Herrmann, N., Swardfager, W., Liu, H., Sham, L., Reim, E. K., & Lanctôt, K. L. (2010). A meta-analysis of cytokines in major depression. Biological Psychiatry, 67(5), 446-457. https://doi.org/10.1016/j.biopsych.2009.09.033
Eisenberger, N. I., Berkman, E. T., Inagaki, T. K., Rameson, L. T., Mashal, N. M., & Irwin, M. R. (2010). Inflammation-induced anhedonia: Endotoxin reduces ventral striatum responses to reward. Biological Psychiatry, 68(8), 748-754. https://doi.org/10.1016/j.biopsych.2010.06.010
Khandaker, G. M., Pearson, R. M., Zammit, S., Lewis, G., & Jones, P. B. (2014). Association of serum interleukin 6 and C-reactive protein in childhood with depression and psychosis in young adult life: A population-based longitudinal study. JAMA Psychiatry, 71(10), 1121-1128. https://doi.org/10.1001/jamapsychiatry.2014.1332
Musselman, D. L., Lawson, D. H., Gumnick, J. F., Manatunga, A. K., Penna, S., Goodkin, R. S., Greiner, K., Nemeroff, C. B., & Miller, A. H. (2001). Paroxetine for the prevention of depression induced by high-dose interferon alfa. New England Journal of Medicine, 344(13), 961-966. https://doi.org/10.1056/NEJM200103293441303
Osimo, E. F., Baxter, L. J., Lewis, G., Jones, P. B., & Khandaker, G. M. (2019). Prevalence of low-grade inflammation in depression: A systematic review and meta-analysis of CRP levels. Psychological Medicine, 49(12), 1958-1970. https://doi.org/10.1017/S0033291719001454
Raison, C. L., Rutherford, R. E., Woolwine, B. J., Shuo, C., Schettler, P., Drake, D. F., Haroon, E., & Miller, A. H. (2013). A randomized controlled trial of the tumor necrosis factor antagonist infliximab for treatment-resistant depression: The role of baseline inflammatory biomarkers. JAMA Psychiatry, 70(1), 31-41. https://doi.org/10.1001/2013.jamapsychiatry.4
Reading the NU 670 Unit 4 instructions
In Unit 4 you build an evidence table around a claim about the biology of a psychiatric disorder. Prompts usually ask you to split a broad claim into testable parts, match each part to the strongest available study, record its design and size, and grade what the design can support. Most templates want a short introduction, the table itself and a paragraph interpreting the pattern. Graders reward tables where each grade follows from the design, not from whether the finding is popular. The interpretation should say which parts of the headline are supported, which are not, and what the patient or public can reasonably take from it. Where a claim cannot be graded, say so and explain why.
How the NU 670 Unit 4 example is put together
A short introduction describes the patient and her handout and sets out three grading levels. Six rows follow, each in the same order: claim, study, design and species, size, finding, what the design can and cannot establish, and grade. The rows move from association to prevalence, time order, experimental effect, drug-induced depression and treatment. A paragraph reads the table as a whole, with a highlighted sentence on where the evidence is strongest and weakest. A separate section explains why the diet claim has no row. The last section turns the grades into three things the author told the patient, including a suggestion to raise her inflammation with her rheumatologist.
Reading the NU670 Unit 4 grading rubric
Evidence tables in this course are usually scored on how the claim is decomposed, the choice of studies, accuracy of the extracted details, the grading logic and the interpretation. Decomposition earns full points when each row tests one claim only. Study choice rewards the strongest design available for that claim, such as a prospective cohort for time order. Accuracy is checked against the sources, so sample sizes and effect estimates must match. The grading logic row looks for grades that follow from design. Interpretation points go to a conclusion that states which parts of the headline hold and which do not, in words a patient could use.
Common NU670 Unit 4 mistakes, and how to avoid them
The most frequent mistake is assigning one grade to the whole headline, which hides the parts that are well supported and those that are not. Another is treating a strong association as evidence of cause. Students often cite a subgroup result, such as infliximab helping patients with high C-reactive protein, as though it were the main finding. Some tables mix several claims in one row, which makes the grade meaningless. Others pick the most famous study rather than the design best suited to the claim. And an interpretation that simply says more research is needed gives the reader nothing to act on. One more trap: leaving a claim out of the table without saying why makes the table look more complete than it is.
Get an NU670 Unit 4 example written to your instructions
An evidence table depends on its claim and its scale, so send the claim your Unit 4 prompt tests and any strength scale your section supplies, plus the rubric. Built to those instructions, the first table is free within 24-48h: each claim split into questions a design can answer, every study classified by design, species and size, and ratings on a footnoted scale. The paper above is an original model document written by our desk, not a submitted student paper and not an official Purdue University Global document.
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NU670 Unit 4 questions, answered
Which evidence hierarchy should the table use?
Whichever your section specifies, and if none is given, a standard hierarchy adapted for mechanism questions works well. State it in a footnote. For biological claims, a well-designed experimental study in people can be more informative about causation than a large observational meta-analysis, so explain any departure from a simple ranking.
How many studies per claim are enough?
Usually one key study per row, chosen because it is the strongest or most cited design for that claim, with a meta-analysis preferred where one exists. Adding several studies per row makes the table hard to read. If the evidence conflicts, cite the best study on each side in the same row and rate the row accordingly.
Where can I find a free NU670 Unit 4 sample paper?
The full NU670 Unit 4 evidence strength table is on this page, with six graded rows, a reading of the pattern, the ungraded diet claim and what the patient was told, plus six references. A table built on your own assigned claim can be written on request.
Does inflammation cause depression according to NU670 Unit 4?
The table finds strong evidence for an association and for short-term mood effects of induced inflammation, moderate evidence that inflammation can come first, and weak evidence that anti-inflammatory treatment relieves depression in general. About a quarter of depressed patients show low-grade inflammation.
What did the infliximab trial show in NU670 Unit 4?
In 60 patients with treatment-resistant depression, infliximab did not differ from placebo overall. Change favored infliximab only in patients with a baseline C-reactive protein above 5 mg/L, a subgroup finding the table grades as weak until it is replicated.