← Research 2019 National Health Interview Survey
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Hidden Dimensions in Chronic Pain: Multiplicative Interactions Between Pain Frequency and Intensity

Chronic pain is the leading cause of disability globally and frequently co-occurs with psychological distress. Despite a widespread assumption that the many dimensions of chronic pain - ranging from intensity, to frequency, to duration of episodes - affect psychological distress, the body of literature examining these effects is sparse. To provide clinicians with the greatest precision for making decisions, we identified the 2019 National Health Interview Survey an ideal source because of its nationally-representative sample, use of the long form PHQ-8 and GAD-87 instruments for depression and anxiety screening, and went beyond the Numeric Pain Rating Scale to capture additional dimensions of the chronic pain that could be leveraged in phenotyping.

We applied a unique chronic pain frequency × intensity × psychological symptom × age cohort gradient to 31,216 participants that was not just an easy-to-understand framework for prioritizing patients for psychological screening, but one that yielded some remarkable findings that have immediate implications on how we identify which patients are at serious risk for psychological distress. Most striking was a result showing that individuals that are unlikely to be immediately recognized as carrying a high risk for depression and anxiety - those with frequent pain, but that they report is only mild - are at 6-7x elevated risk over baseline for depression and anxiety in some age groups.

In a clinical paradigm that focuses primarily on asking "how bad does it hurt?", it is highly likely that patients are leaving appointments with elevated distress, without anyone having recognized they were any more risky than those with those reporting no pain symptoms at all.

Initial Findings

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Initial Results

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Table 1 — Population Descriptives
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Characteristic n (unweighted) % (weighted) 95% CI
Total sample21,161——
Pain Frequency
Never / rarely14,28068.2%[67.1, 69.3]
Some days4,10319.1%[18.2, 20.0]
Most days / every day2,77812.7%[12.0, 13.5]
Table 2 — Adjusted Risk Ratios (Supplementary Analysis)
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Controlled for demographics, BMI, health behaviors, and health context. Shown below are clinical-threshold outcomes (PHQ-8 ≥ 10, GAD-7 ≥ 10); full results across all six outcomes available in CSV.

Age Group Pain Profile Outcome aRR 95% CI Sig
Emerging Adults (18–29)
Intermittent mildPHQ-81.97(1.20–3.22)**
Intermittent mod-severePHQ-83.90(2.63–5.76)***
Frequent mildPHQ-87.15(3.73–13.72)***
Frequent mod-severePHQ-88.95(6.05–13.25)***
Intermittent mildGAD-71.70(1.12–2.59)*
Intermittent mod-severeGAD-72.92(2.04–4.18)***
Frequent mildGAD-76.58(3.67–11.81)***
Frequent mod-severeGAD-75.71(3.99–8.17)***
Young Adults (30–44)
Intermittent mildPHQ-81.72(1.17–2.51)**
Intermittent mod-severePHQ-83.18(2.24–4.52)***
Frequent mildPHQ-85.29(3.19–8.78)***
Frequent mod-severePHQ-88.34(6.06–11.48)***
Intermittent mildGAD-71.93(1.34–2.79)***
Intermittent mod-severeGAD-73.13(2.22–4.42)***
Frequent mildGAD-74.20(2.43–7.25)***
Frequent mod-severeGAD-77.57(5.59–10.26)***
Middle Adults (45–64)
Intermittent mildPHQ-81.57(0.99–2.49)
Intermittent mod-severePHQ-82.70(1.84–3.96)***
Frequent mildPHQ-83.16(1.95–5.13)***
Frequent mod-severePHQ-89.11(6.39–12.99)***
Intermittent mildGAD-71.45(0.90–2.32)
Intermittent mod-severeGAD-72.38(1.56–3.63)***
Frequent mildGAD-72.67(1.56–4.59)***
Frequent mod-severeGAD-77.97(5.43–11.69)***
Older Adults (65+)
Intermittent mildPHQ-81.30(0.85–1.99)
Intermittent mod-severePHQ-82.52(1.57–4.03)***
Frequent mildPHQ-82.65(1.61–4.36)***
Frequent mod-severePHQ-85.50(3.77–8.03)***
Intermittent mildGAD-70.71(0.41–1.23)
Intermittent mod-severeGAD-72.05(1.16–3.62)*
Frequent mildGAD-73.02(1.46–6.27)**
Frequent mod-severeGAD-75.76(3.67–9.05)***

Reference group: No pain within each age group. * p < .05, ** p < .01, *** p < .001

Table 3 — Bonferroni-Corrected Significance
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Bonferroni correction applied across 80 simultaneous tests (αadjusted = .000625), showing 71 tests still met the highest standards. Shown below are clinical-threshold outcomes; full correction results across all outcomes available in CSV.

Age Group Pain Profile Outcome aRR 95% CI Raw p Bonf.
Emerging Adults (18–29)
Intermittent mildPHQ-82.03(1.25–3.31).005
Intermittent mod-severePHQ-84.25(2.89–6.26)< .001✓
Frequent mildPHQ-87.10(3.72–13.56)< .001✓
Frequent mod-severePHQ-89.61(6.61–13.98)< .001✓
Intermittent mildGAD-71.73(1.13–2.62).011
Intermittent mod-severeGAD-73.13(2.20–4.46)< .001✓
Frequent mildGAD-76.56(3.69–11.66)< .001✓
Frequent mod-severeGAD-76.37(4.50–9.02)< .001✓
Young Adults (30–44)
Intermittent mildPHQ-81.77(1.21–2.57).003
Intermittent mod-severePHQ-83.34(2.38–4.70)< .001✓
Frequent mildPHQ-85.92(3.60–9.73)< .001✓
Frequent mod-severePHQ-89.51(7.09–12.76)< .001✓
Intermittent mildGAD-71.96(1.35–2.82)< .001✓
Intermittent mod-severeGAD-73.26(2.34–4.54)< .001✓
Frequent mildGAD-74.80(2.79–8.25)< .001✓
Frequent mod-severeGAD-78.78(6.62–11.66)< .001✓
Middle Adults (45–64)
Intermittent mildPHQ-81.64(1.04–2.58).032
Intermittent mod-severePHQ-82.96(2.04–4.29)< .001✓
Frequent mildPHQ-83.43(2.13–5.53)< .001✓
Frequent mod-severePHQ-810.75(7.66–15.09)< .001✓
Intermittent mildGAD-71.52(0.95–2.43).079
Intermittent mod-severeGAD-72.54(1.68–3.84)< .001✓
Frequent mildGAD-72.79(1.63–4.77)< .001✓
Frequent mod-severeGAD-79.02(6.27–12.98)< .001✓
Older Adults (65+)
Intermittent mildPHQ-81.42(0.93–2.16).106
Intermittent mod-severePHQ-82.80(1.76–4.45)< .001✓
Frequent mildPHQ-83.00(1.84–4.89)< .001✓
Frequent mod-severePHQ-86.65(4.56–9.71)< .001✓
Intermittent mildGAD-70.77(0.45–1.32).336
Intermittent mod-severeGAD-72.27(1.32–3.92).003
Frequent mildGAD-73.24(1.58–6.67).001
Frequent mod-severeGAD-76.67(4.34–10.23)< .001✓

✓ = Survives Bonferroni correction (padjusted < .05). Reference group: No pain within each age group.

Table 4 — E-Values for Unmeasured Confounding
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E-values quantify the minimum strength an unmeasured confounder would need — in its associations with both the exposure and the outcome — to explain away each observed association. Shown below are clinical-threshold outcomes; full results across all outcomes available in CSV.

Age Group Outcome Pain Profile aRR 95% CI E-value (point) E-value (CI)
Emerging Adults (18–29)
PHQ-8Frequent mod-severe9.61(6.61–13.98)18.7112.70
PHQ-8Frequent mild7.10(3.72–13.56)13.686.90
PHQ-8Intermittent mod-severe4.25(2.89–6.26)7.975.23
PHQ-8Intermittent mild2.03(1.25–3.31)3.481.81
GAD-7Frequent mild6.56(3.69–11.66)12.606.84
GAD-7Frequent mod-severe6.37(4.50–9.02)12.228.47
GAD-7Intermittent mod-severe3.13(2.20–4.46)5.713.82
GAD-7Intermittent mild1.73(1.13–2.62)2.851.51
Young Adults (30–44)
PHQ-8Frequent mod-severe9.51(7.09–12.76)18.5113.66
PHQ-8Frequent mild5.92(3.60–9.73)11.326.66
PHQ-8Intermittent mod-severe3.34(2.38–4.70)6.144.19
PHQ-8Intermittent mild1.77(1.21–2.57)2.941.71
GAD-7Frequent mod-severe8.78(6.62–11.66)17.0412.72
GAD-7Frequent mild4.80(2.79–8.25)9.075.02
GAD-7Intermittent mod-severe3.26(2.34–4.54)5.974.11
GAD-7Intermittent mild1.96(1.35–2.82)3.332.04
Middle Adults (45–64)
PHQ-8Frequent mod-severe10.75(7.66–15.09)20.9914.80
PHQ-8Frequent mild3.43(2.13–5.53)6.323.68
PHQ-8Intermittent mod-severe2.96(2.04–4.29)5.373.50
PHQ-8Intermittent mild1.64(1.04–2.58)2.661.24
GAD-7Frequent mod-severe9.02(6.27–12.98)17.5312.02
GAD-7Frequent mild2.79(1.63–4.77)5.022.64
GAD-7Intermittent mod-severe2.54(1.68–3.84)4.522.75
GAD-7Intermittent mild1.52(0.95–2.43)2.401.00
Older Adults (65+)
PHQ-8Frequent mod-severe6.65(4.56–9.71)12.788.59
PHQ-8Frequent mild3.00(1.84–4.89)5.453.08
PHQ-8Intermittent mod-severe2.80(1.76–4.45)5.042.92
PHQ-8Intermittent mild1.42(0.93–2.16)2.201.00
GAD-7Frequent mod-severe6.67(4.34–10.23)12.828.15
GAD-7Frequent mild3.24(1.58–6.67)5.932.54
GAD-7Intermittent mod-severe2.27(1.32–3.92)3.971.97
GAD-7Intermittent mild0.77(0.45–1.32)1.001.00

Higher E-values indicate greater robustness to unmeasured confounding. E-value (CI) represents the lower confidence bound — the more conservative estimate.

Table 5 — Sample Sizes by Age Group and Pain Profile
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Unweighted cell counts for each analytic combination. Clinical outcome columns show the number of individuals meeting or exceeding the clinical threshold within each cell.

Age Group Pain Profile n PHQ ≥ 10 GAD ≥ 10
Emerging Adults (18–29)
No pain2,3776988
Intermittent mild8614451
Intermittent mod-severe7379997
Frequent mild721317
Frequent mod-severe3329992
Young Adults (30–44)
No pain3,4677887
Intermittent mild1,7026668
Intermittent mod-severe1,1279089
Frequent mild1972419
Frequent mod-severe885230230
Middle Adults (45–64)
No pain3,5136056
Intermittent mild2,4046156
Intermittent mod-severe1,64110985
Frequent mild4713727
Frequent mod-severe2,346572463
Older Adults (65+)
No pain2,6454433
Intermittent mild2,2365925
Intermittent mod-severe1,3427241
Frequent mild5653017
Frequent mod-severe2,296329224
Literature Review

Chronic pain and psychological distress co-occur in over 100 million U.S. adults, at an estimated annual cost of $600 billion. Pain prevalence rises with age — from roughly 18% in young adults to over 30% in older adults — but whether pain's psychological impact follows the same trajectory remains unknown. Decades of research link pain to depression, anxiety, and functional impairment, yet no study has used consistent methodology to map how these relationships change across the adult lifespan. Without lifecycle comparisons, clinical screening may misidentify who is actually at risk.

The full scope of these dimensions can be found in the complete literature review.

Working Abstract

Background: Clinical assessment of chronic pain emphasizes intensity, yet pain frequency may independently contribute to psychological burden. We examined whether pain frequency confers psychological risk beyond intensity effects, how this relationship varies across the adult lifespan, and whether observed associations reflect treatment-seeking behavior or independent risk.

Methods: Cross-sectional analysis of 31,216 adults from the 2019 National Health Interview Survey. Pain profiles combined frequency and intensity into five categories. Outcomes included dysphoria, anhedonia, somatic symptoms, clinical depression, and clinical anxiety. Survey-weighted quasipoisson regression estimated prevalence risk ratios stratified by developmental stage. Treatment stratification isolated associations among individuals not receiving psychiatric treatment.

Results: Frequent mild pain conferred psychological risk equal to or exceeding intermittent moderate-severe pain, particularly in younger adults. This pattern attenuated with age; older adults showed comparable risk across these profiles. When analyses were restricted to untreated individuals, the frequent mild pain association strengthened rather than diminished, ruling out treatment-seeking as an alternative explanation. Despite elevated psychological risk, only 15% of emerging adults with frequent mild pain received psychiatric treatment — the only pain profile where distress exceeded treatment utilization.

Conclusions: Pain frequency represents an independent dimension of psychological risk that interacts with intensity differently across developmental stages. Frequent mild pain in emerging adults constitutes a clinically under-recognized phenotype: high psychological burden combined with low treatment engagement. Clinical screening should assess pain frequency alongside intensity, as "mild but constant" pain may warrant greater attention than "severe but occasional" pain, particularly in younger adults.

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