Vulnerability to stress-related sleep disturbance and insomnia: investigating the link with comorbid depressive symptoms
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= 2.97) from the Colorado Longitudinal Twin Study and Community Twin Study. Results indicated that greater sleep reactivity was significantly associated with elevated depressive symptoms, and that this link was partially mediated by insomnia. This is one of the first studies to demonstrate an independent association between sleep reactivity and depressive symptomatology. These findings suggest that a greater sensitivity to stress-related sleep disturbance may also be a predisposing factor to depression, and highlight the need for a better understanding of sleep reactivity, as it may represent a more global vulnerability construct.
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The strong association of depressive and insomnia symptoms is consistent with evidence supporting their high level of comorbidity.
“The strong association of depressive and insomnia symptoms is consistent with evidence supporting their high level of comorbidity [35, 62–65].”
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Cites
Diagnostic and Statistical Manual of Mental Disorders
Williams, J. B. W., & First, M. B. (2013) · Oxford University Press eBooks · doi:10.1093/acrefore/9780199975839.013.104 · Cited by 109,841 · see citing works
The CES-D Scale: A Self-Report Depression Scale for Research in the General Population
Radloff, L. S. (1977) · Applied Psychological Measurement · doi:10.1177/014662167700100306 · Cited by 53,267 · see citing works
Asymptotic Confidence Intervals for Indirect Effects in Structural Equation Models
Sobel, M. E. (1982) · Sociological Methodology · doi:10.2307/270723 · Cited by 12,810 · see citing works
Epidemiology of insomnia: what we know and what we still need to learn
Ohayon, M. M. (2002) · Sleep Medicine Reviews · doi:10.1053/smrv.2002.0186 · Cited by 3,743 · cited 2× · see citing works
“Keywords sleep reactivity; insomnia; depressive symptoms; stress Insomnia is a major source of daytime impairment (Riedel & Lichstein, 2000; Drake, Vargas, Roth, & Friedman, 2014) and is associated with a number of negative health consequences (Ohayon, 2002).”
BackgroundResultGenetic Epidemiology of Major Depression: Review and Meta-Analysis
Sullivan, P. F., Neale, M. C., & Kendler, K. S. (2000) · American Journal of Psychiatry · doi:10.1176/appi.ajp.157.10.1552 · Cited by 3,431 · see citing works
Hammen, C. (2005) · Annual Review of Clinical Psychology · doi:10.1146/annurev.clinpsy.1.102803.143938 · Cited by 2,979 · see citing works
Baglioni, C., Battagliese, G., Feige, B., Spiegelhalder, K., Nissen, C., Voderholzer, U., Lombardo, C., & Riemann, D. (2011) · Journal of Affective Disorders · doi:10.1016/j.jad.2011.01.011 · Cited by 2,779 · see citing works
Depression and cortisol responses to psychological stress: A meta-analysis
Burke, H. M., Davis, M. C., Otte, C., & Mohr, D. C. (2005) · Psychoneuroendocrinology · doi:10.1016/j.psyneuen.2005.02.010 · Cited by 1,194 · see citing works
Prevalence, course, and comorbidity of insomnia and depression in young adults.
Buysse, D. J., Angst, J., Gamma, A., Ajdacic, V., Eich, D., & Rössler, W. (2008) · Sleep · doi:10.1093/sleep/31.4.473 · Cited by 858 · see citing works
Measurement of depressive symptoms in cancer patients
Hann, D., Winter, K., & Jacobsen, P. (1999) · Journal of Psychosomatic Research · doi:10.1016/s0022-3999(99)00004-5 · Cited by 822 · see citing works
Role of Stress, Arousal, and Coping Skills in Primary Insomnia
Morin, C. M., Rodrigue, S., & Ivers, H. (2003) · Psychosomatic Medicine · doi:10.1097/01.psy.0000030391.09558.a3 · Cited by 739 · see citing works
Sleep disturbances, work stress and work hours
Åkerstedt, T., Knutsson, A., Westerholm, P., Theorell, T., Alfredsson, L., & Kecklund, G. (2002) · Journal of Psychosomatic Research · doi:10.1016/s0022-3999(02)00333-1 · Cited by 716 · see citing works
Monroe, S. M., & Harkness, K. L. (2005) · Psychological Review · doi:10.1037/0033-295x.112.2.417 · Cited by 693 · see citing works
Primary insomnia: a risk factor to develop depression?
Riemann, D. (2003) · Journal of Affective Disorders · doi:10.1016/s0165-0327(02)00072-1 · Cited by 641 · see citing works
De Raedt, R., & Koster, E. H. W. (2010) · Cognitive, Affective, & Behavioral Neuroscience · doi:10.3758/cabn.10.1.50 · Cited by 583 · see citing works
Roth, T. G., Coulouvrat, C., Hajak, G., Lakoma, M. D., Sampson, N. A., Shahly, V., Shillington, A. C., Stephenson, J. J., Walsh, J. K., & Kessler, R. C. (2011) · Biological Psychiatry · doi:10.1016/j.biopsych.2010.10.023 · Cited by 477 · see citing works
Vulnerability to Stress-related Sleep Disturbance and Hyperarousal
Drake, C., Richardson, G., Roehrs, T., Scofield, H., & Roth, T. (2004) · Sleep · doi:10.1093/sleep/27.2.285 · Cited by 469 · see citing works
Devins, G. M., Orme, C. M., Costello, C. G., Binik, Y. M., Frizzell, B., Stam, H. J., & Pullin, W. M. (1988) · Psychology & Health · doi:10.1080/08870448808400349 · Cited by 412 · see citing works
Stress and Sleep Reactivity: A Prospective Investigation of the Stress-Diathesis Model of Insomnia
Drake, C. L., Pillai, V., & Roth, T. G. (2014) · SLEEP · doi:10.5665/sleep.3916 · Cited by 347 · see citing works
Insomnia and daytime functioning
Riedel, B. W., & Lichstein, K. L. (2000) · Sleep Medicine Reviews · doi:10.1053/smrv.1999.0074 · Cited by 309 · see citing works
Chronic Insomnia and the Stress System
Basta, M., Chrousos, G. P., Vela‐Bueno, A., & Vgontzas, A. N. (2007) · Sleep Medicine Clinics · doi:10.1016/j.jsmc.2007.04.002 · Cited by 294 · see citing works
Comorbidity of mental and insomnia disorders in the general population
Ohayon, M. M., Caulet, M., & Lemoine, P. (1998) · Comprehensive Psychiatry · doi:10.1016/s0010-440x(98)90059-1 · Cited by 261 · see citing works
Intra-individual variability in sleep duration and fragmentation: Associations with stress
Mezick, E. J., Matthews, K. A., Hall, M. H., Kamarck, T. W., Buysse, D. J., Owens, J. F., & Reís, S. E. (2009) · Psychoneuroendocrinology · doi:10.1016/j.psyneuen.2009.04.005 · Cited by 239 · see citing works
Cognitive-Emotional Hyperarousal as a Premorbid Characteristic of Individuals Vulnerable to Insomnia
Fernández-Mendoza, J., Vela-Bueno, A., Vgontzas, A. N., Ramos-Platón, M. J., Olavarrieta-Bernardino, S., Bixler, E. O., & De la Cruz-Troca, J. J. (2010) · Psychosomatic Medicine · doi:10.1097/psy.0b013e3181d75319 · Cited by 234 · see citing works
Genetic and Environmental Influences on Insomnia, Daytime Sleepiness, and Obesity in Twins
Watson, N. F., Goldberg, J. H., Arguelles, L., & Buchwald, D. (2006) · SLEEP · doi:10.1093/sleep/29.5.645 · Cited by 166 · see citing works
Sleep Reactivity and Insomnia: Genetic and Environmental Influences
Drake, C. L., Friedman, N. P., Wright, K. P., & Roth, T. (2011) · Sleep · doi:10.5665/sleep.1234 · Cited by 166 · see citing works
Family Conflict in Childhood: A Predictor of Later Insomnia
Gregory, A. M., Caspi, A., Moffitt, T. E., & Poulton, R. (2006) · SLEEP · doi:10.1093/sleep/29.8.1063 · Cited by 157 · see citing works
Cognitive Vulnerability to Depression: Theory and Evidence
Abramson, L. Y., Alloy, L. B., Hogan, M. E., Whitehouse, W. G., Donovan, P., Rose, D. T., Panzarella, C., & Raniere, D. (1999) · Journal of Cognitive Psychotherapy · doi:10.1891/0889-8391.13.1.5 · Cited by 151 · see citing works
Financial strain is a significant correlate of sleep continuity disturbances in late-life
Hall, M. H., Buysse, D. J., Nofzinger, E. A., Reynolds, C. F., Thompson, W. K., Mazumdar, S., & Monk, T. H. (2007) · Biological Psychology · doi:10.1016/j.biopsycho.2007.10.012 · Cited by 141 · see citing works
Pillai, V., Roth, T. G., Mullins, H. M., & Drake, C. L. (2014) · SLEEP · doi:10.5665/sleep.3838 · Cited by 130 · see citing works
Morris, M. C., Rao, U., & Garber, J. (2012) · Journal of Affective Disorders · doi:10.1016/j.jad.2012.05.059 · Cited by 102 · see citing works
Confirmatory Factor Analysis of the Pittsburgh Sleep Quality Index in Rheumatoid Arthritis Patients
Nicassio, P., Ormseth, S. R., Custodio, M. K., Olmstead, R., Weisman, M., & Irwin, M. R. (2013) · Behavioural Sleep Medicine · doi:10.1080/15402002.2012.720315 · Cited by 98 · see citing works
Family life stress and insomnia symptoms in a prospective evaluation of young adults.
Bernert, R. A., Merrill, K. A., Braithwaite, S. R., Van Orden, K. A., & Joiner, T. E. (2007) · Journal of Family Psychology · doi:10.1037/0893-3200.21.1.58 · Cited by 93 · see citing works
Colorado Twin Registry: An Update
Rhea, S. A., Gross, A. A., Haberstick, B. C., & Corley, R. P. (2012) · Twin Research and Human Genetics · doi:10.1017/thg.2012.93 · Cited by 77 · see citing works
Vulnerability to insomnia: The role of familial aggregation
Drake, C. L., Scofield, H., & Roth, T. G. (2007) · Sleep Medicine · doi:10.1016/j.sleep.2007.04.012 · Cited by 74 · see citing works
Dissecting the impact of sleep and stress on the cortisol awakening response in young adults
Vargas, I., & Lopez‐Duran, N. L. (2013) · Psychoneuroendocrinology · doi:10.1016/j.psyneuen.2013.10.009 · Cited by 59 · see citing works
Nakajima, S., Okajima, I., Sasai, T., Kobayashi, M., Furudate, N., Drake, C. L., Roth, T. G., & Inoue, Y. (2013) · Sleep Medicine · doi:10.1016/j.sleep.2013.09.022 · Cited by 58 · see citing works
Predisposition in the Evolution of Insomnia: Evidence, Potential Mechanisms, and Future Directions
Drake, C. L., & Roth, T. G. (2006) · Sleep Medicine Clinics · doi:10.1016/j.jsmc.2006.06.005 · Cited by 51 · see citing works
Williams, P., Cribbet, M. R., Rau, H., Gunn, H. E., & Czajkowski, L. A. (2013) · Annals of Behavioral Medicine · doi:10.1007/s12160-013-9482-x · Cited by 48 · see citing works
Yang, C., Chou, C. P.-W., & Hsiao, F. (2011) · Behavioral Sleep Medicine · doi:10.1080/15402002.2011.557990 · Cited by 46 · see citing works
Cognitive Vulnerability to Depression: Exploring Risk and Resilience
Haeffel, G. J., & Grigorenko, E. L. (2007) · Child and Adolescent Psychiatric Clinics of North America · doi:10.1016/j.chc.2006.11.005 · Cited by 45 · see citing works
Cortisol response to psychosocial stress during a depressive episode and remission
Morris, M. C., & Rao, U. (2014) · Stress · doi:10.3109/10253890.2013.857398 · Cited by 34 · see citing works
中島, 俊. (2014) · Institutional Repositories DataBase (IRDB) · Cited by 30 · see citing works
Drake, C. L., Vargas, I., Roth, T. G., & Friedman, N. P. (2014) · Behavioral Sleep Medicine · doi:10.1080/15402002.2014.880345 · Cited by 18 · see citing works
Haynes, P. L., Ancoli‐Israel, S., Walter, C. M., & McQuaid, J. R. (2011) · Cognitive Therapy and Research · doi:10.1007/s10608-011-9416-5 · Cited by 8 · see citing works
Information processing during sleep and stress‐related sleep vulnerability
Lin, Y., Jen, C.-H., & Yang, C. (2014) · Psychiatry and Clinical Neurosciences · doi:10.1111/pcn.12206 · Cited by 7 · see citing works
Jarrin, D. C., Chen, I., Ivers, H., & Morin, C. M. (2013) · Sleep Medicine · doi:10.1016/j.sleep.2013.11.368 · Cited by 4 · see citing works
Flagged first, then by citations
Research works printed but not linked: 1
- Jefferson C Roehrs T Roth T Drake C 2005 Sleep reactivity to stress in insomniacs Proceedings of the 1st Congress of the World Association of Sleep Medicine 79 82
Cited by
Sorted by citations
Kalmbach, D. A., Anderson, J. R., & Drake, C. L. (2018) · Journal of Sleep Research · doi:10.1111/jsr.12710 · Cited by 620 · see citing works
Heart Rate Variability, Sleep Quality, and Depression in the Context of Chronic Stress
da Estrela, C., McGrath, J., Booij, L., & Gouin, J.-P. (2021) · Annals of Behavioral Medicine · doi:10.1093/abm/kaaa039 · Cited by 118 · see citing works
Insomnia and depression: clinical associations and possible mechanistic links
Vargas, I., & Perlis, M. L. (2020) · Current Opinion in Psychology · doi:10.1016/j.copsyc.2019.11.004 · Cited by 95 · see citing works
Daucourt, M. C., Erbeli, F., Little, C. W., Haughbrook, R., & Hart, S. A. (2019) · Scientific Studies of Reading · doi:10.1080/10888438.2019.1631827 · Cited by 73 · see citing works
Das‐Friebel, A., Lenneis, A., Realo, A., Sanborn, A., Tang, N. K. Y., Wolke, D., von Mühlenen, A., & Lemola, S. (2020) · Journal of Child Psychology and Psychiatry · doi:10.1111/jcpp.13326 · Cited by 71 · see citing works
Palagini, L., Cipollone, G., Masci, I., Novi, M., Caruso, D., Kalmbach, D. A., & Drake, C. L. (2019) · Sleep Medicine · doi:10.1016/j.sleep.2019.01.009 · Cited by 67 · see citing works
Lind, M. J., & Gehrman, P. (2016) · Brain Sciences · doi:10.3390/brainsci6040064 · Cited by 64 · see citing works
The Role of Brain-Derived Neurotrophic Factor in Immune-Related Diseases: A Narrative Review
Sochal, M., Ditmer, M., Gabryelska, A., & Białasiewicz, P. (2022) · Journal of Clinical Medicine · doi:10.3390/jcm11206023 · Cited by 52 · see citing works
Park, I., Oh, S. M., Lee, K. H., Kim, S., Jeon, J. E., Lee, H. Y., Jeon, S., Kim, S. J., & Lee, Y. J. (2020) · Psychiatry Investigation · doi:10.30773/pi.2019.0181 · Cited by 46 · see citing works
Sleep system sensitization: evidence for changing roles of etiological factors in insomnia
Kalmbach, D. A., Pillai, V., Arnedt, J. T., Anderson, J. R., & Drake, C. L. (2016) · Sleep Medicine · doi:10.1016/j.sleep.2016.02.005 · Cited by 44 · see citing works
Daily reactivity to stress and sleep disturbances: unique risk factors for insomnia
Yoo, J., Slavish, D. C., Dietch, J. R., Kelly, K. S., Ruggero, C. J., & Taylor, D. J. (2022) · SLEEP · doi:10.1093/sleep/zsac256 · Cited by 40 · see citing works
Bishop, M., Gise, J., Donati, M. R., Shneider, C. E., Aylward, B. S., & Cohen, L. L. (2019) · Journal of Pediatric Psychology · doi:10.1093/jpepsy/jsz026 · Cited by 39 · see citing works
Association of stress-related sleep disturbance with psychiatric symptoms among pregnant women
Sánchez, S., Friedman, L. E., Rondon, M. B., Drake, C., Williams, M. A., & Gelaye, B. (2020) · Sleep Medicine · doi:10.1016/j.sleep.2020.02.007 · Cited by 34 · see citing works
Walker, J. L., Vargas, I., Drake, C. L., Ellis, J. G., Muench, A., & Perlis, M. L. (2022) · SLEEP · doi:10.1093/sleep/zsac149 · Cited by 30 · see citing works
Shi, X., Qi, H., Wang, S., Li, Z., Li, Z., & Fan, F. (2021) · Frontiers in Psychiatry · doi:10.3389/fpsyt.2021.748064 · Cited by 19 · see citing works
Lutin, E., Schiweck, C., Cornelis, J. P., Raedt, W. D., Reif, A., Vrieze, E., Claes, S. J., & Hoof, C. A. V. (2022) · Frontiers in Psychiatry · doi:10.3389/fpsyt.2022.1022298 · Cited by 16 · see citing works
Vargas, I., Nguyen, A., Haeffel, G. J., & Drake, C. L. (2020) · Journal of Affective Disorders Reports · doi:10.1016/j.jadr.2020.100010 · Cited by 16 · see citing works
Wulf Rössler, A., Ajdacic‐Gross, V., Glozier, N., Rodgers, S., Haker, H., & Müller, M. (2017) · Comprehensive Psychiatry · doi:10.1016/j.comppsych.2017.07.009 · Cited by 14 · see citing works
Marques, D. R., Gomes, A. A., Drake, C. L., Roth, T. G., & de Azevedo, M. H. P. (2016) · Behavioral Sleep Medicine · doi:10.1080/15402002.2016.1210151 · Cited by 14 · see citing works
Petrie, K. A., Messman, B., Slavish, D. C., Moore, E. W. G., & Petrie, T. A. (2023) · Psychology of sport and exercise · doi:10.1016/j.psychsport.2023.102393 · Cited by 15 · see citing works
Meaklim, H., Le, F., Drummond, S. P. A., Bains, S. K., Varma, P., Junge, M. F., & Jackson, M. L. (2024) · Sleep · doi:10.1093/sleep/zsae028 · Cited by 10 · see citing works
“The strong association of depressive and insomnia symptoms is consistent with evidence supporting their high level of comorbidity [35, 62–65].”
ResultKara, M., Şahin, S., Rabbani, F., Öztaş, E., Hasbal‐Celikok, G., Kanımdan, E., Koçyiğit, A., Kanwal, A., Wade, U., Yakunina, A., et al. (2024) · Frontiers in Molecular Biosciences · doi:10.3389/fmolb.2024.1359177 · Cited by 10 · see citing works
Yang, T., Derks, E. M., & Thorp, J. G. (2025) · Journal of Affective Disorders · doi:10.1016/j.jad.2025.120112 · Cited by 6 · see citing works
Dougherty, E. N., Johnson, N. K., Badillo, K., & Haedt‐Matt, A. A. (2021) · Journal of American College Health · doi:10.1080/07448481.2021.1967359 · Cited by 5 · see citing works
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Herrick, D. D., & Sateia, M. J. (2016) · Psychiatric Annals · doi:10.3928/00485713-20160121-01 · Cited by 4 · see citing works
Hachenberger, J., ten Brink, M., Kerkhoff, D., Baron, S., Schabus, M., & Lemola, S. (2025) · International Journal of Clinical and Health Psychology · doi:10.1016/j.ijchp.2025.100648 · Cited by 4 · see citing works
Gauld, C., Tebeka, S., Geoffroy, P. A., Fourneret, P., Mazer, N., Peyre, H., & Dubertret, C. (2024) · Journal of Affective Disorders · doi:10.1016/j.jad.2024.06.089 · Cited by 2 · see citing works
Tong, J., Wang, Y., Liu, H., Li, Y., Pan, J., Fan, D., & Zhao, H. (2024) · Guidelines and Standards of Chinese Medicine · doi:10.1097/gscm.0000000000000038 · Cited by 1 · see citing works
Kostin, A., Suntsova, N., Kumar, S., & Gvilia, I. (2025) · Stress · doi:10.1080/10253890.2025.2465393 · Cited by 2 · see citing works
Research on Treating Insomnia Accompanied With Depression by Mongolian Medical Warm Acupuncture
Bao, L., Li, S., Jin, Q., Si, L., & Bo, A. (2018) · Physikalische Medizin Rehabilitationsmedizin Kurortmedizin · doi:10.1055/a-0658-1675 · Cited by 1 · see citing works
Comorbid Psychiatric Illnesses
Thorsteinsson, E., & Brown, R. F. (2019) · Springer eBooks · doi:10.1007/978-3-030-32545-9_6 · Cited by 1 · see citing works
Spatial Learning Paradigm Can Increase Post-Stress Total Time of REM Sleep in Immobilized Rats
Sharifian, F. E., Bahrami, F., & Bahari, Z. (2019) · Journal of Advances in Medical and Biomedical Research · doi:10.30699/jambs.27.123.9
Change of Heart: Parenting Stress and Distress, and Associations with Heart Rate Variability
da Estrela, C. (2020) · Spectrum Research Repository (Concordia University)
Komorbide psychiatrische Erkrankungen
Thorsteinsson, E., & Brown, R. F. (2024) · Springer eBooks · doi:10.1007/978-3-031-55637-1_6
Gao, Y., & Yang, J. (2025) · Psychology Health & Medicine · doi:10.1080/13548506.2025.2575409
Seki, T., Shimura, A., Nakajima, K., Kikkawa, M., Morishita, C., Tamada, Y., Honyashiki, M., Masuya, J., & Inoue, T. (2025) · European Journal of Sport Science · doi:10.1002/ejsc.70111
Matar, H. I., Alrabadi, B., Alrishoud, D., Yassin, A. R. B., Almuqasqas, T., Libdeh, D. A., Aldalati, A. Y., Rababah, A. O., & Bandak, N. (2026) · Sleep and Vigilance · doi:10.1007/s41782-026-00361-x
- Authors
- Vargas, I., Friedman, N. P., & Drake, C. L.
- Affiliations
- University of Colorado Boulder (US)
- Henry Ford Health (US)
- Venue
- Translational Issues in Psychological Science
- Published
- 2015-03
- Volume
- 1
- Issue
- 1
- Pages
- 57-66
- ISSN
- 2332-2136 (ISSN-L)
- 2332-2179
- PMC
- PMC4406050
- OpenAlex
- W2332192145
- Cited by
- 37
- References
- 46
- Citations by year
- 2026: 1 · 2025: 5 · 2024: 5 · 2023: 1 · 2022: 4 · 2021: 2 · 2020: 6 · 2019: 6 · 2018: 2 · 2017: 1 · 2016: 4
- FWCI
- 3.53
- Type
- journal article
- Language
- en
- Open access
- hybrid
- doi.org
- Locations
- Translational Issues in Psychological Science (publishedVersion, other-oa)
- PubMed (publishedVersion)
- PubMed Central (acceptedVersion)
- Funders
- Henry Ford Hospital
- National Institutes of Health (MH063207; DA011015)
- Topics
- Social Sciences › Psychology › Experimental and Cognitive Psychology › Sleep and related disorders
- Social Sciences › Psychology › Experimental and Cognitive Psychology › Anxiety, Depression, Psychometrics, Treatment, Cognitive Processes
- Life Sciences › Neuroscience › Cognitive Neuroscience › Sleep and Wakefulness Research
- Keywords
- sleep reactivity, insomnia, depressive symptoms, depression vulnerability, mediation, twin studies, genetic susceptibility
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