TARGET ARTICLE: Explaining the Relationships Between Religious Involvement and Health
Abstract
There is increasing research evidence that religious involvement is associated both cross-sectionally and prospectively with better physical health, better mental health, and longer survival. These relationships remain substantial in size and statistically significant with other risk and protective factors for morbidity and mortality statistically controlled. In this article, we review the social and psychological factors that have been hypothesized to explain the health-promoting effects of religious involvement. The four potential psychosocial mechanisms that have received empirical attention are health practices, social support, psychosocial resources such as self-esteem and self-efficacy, and belief structures such as sense of coherence. Evidence concerning these potential mediators is mixed and inconsistent, suggesting there is more to be learned about the pathways by which religion affects health. Other possible explanations for the salubrious effects of religious involvement on health and longevity are discussed.
Integrity signals
Registry
Cites
Statistics
Claims the paper makes
Claims other papers make about this one
Each is checked against this paper’s own text: does it say what the citing paper says it does?
The relationships between religiosity and mental health and freedom from coronary disease and certain cancers typically are positive.
“A large literature indicates that the relationships between religiosity and mental health and freedom from coronary disease and certain cancers typically are positive (George et al. 2002; Koenig 1997).”
From Parasite-stress promotes in-group assortative sociality: The cases of strong family ties and heightened religiosity (2012) · cites this paper as George et al. 2002
Little is known about the mediators of the positive relationship between religiosity and health.
“As George et al. (2002) emphasize, despite a great deal of research, little is known about the mediators of the positive relationship between religiosity and health.”
From Parasite-stress promotes in-group assortative sociality: The cases of strong family ties and heightened religiosity (2012) · cites this paper as George et al. 2002
Effects of RS-related social support are inconsistent, and although this type of social support is consistently related to mortality, it often functions as an independent predictor rather than as a mediator.
“However, effects of RS-related social support are inconsistent (George et al., 2002), and it appears that although this type of social support is consistently related to mortality, it often functions as an independent predictor rather than as a mediator.”
From Advancing our understanding of religion and spirituality in the context of behavioral medicine (2017) · cites this paper as George et al., 2002
When studies of the service attendance-mortality link control for social support, relations between attendance and mortality often become substantially weaker, indicating that social support mediates at least some of the relationship of RS with health.
“When studies of the service attendance-mortality link control for its influence, relations between attendance and mortality often become substantially weaker (George et al., 2002), indicating that social support mediates at least some of the relationship of RS with health.”
From Advancing our understanding of religion and spirituality in the context of behavioral medicine (2017) · cites this paper as George et al., 2002
Cites
Social Relationships and Health
House, J. S., Landis, K. R., & Umberson, D. (1988) · Science · doi:10.1126/science.3399889 · Cited by 7,073 · see citing works
Pearlin, L. I., Menaghan, E. G., Lieberman, M. A., & Mullan, J. T. (1981) · Journal of Health and Social Behavior · doi:10.2307/2136676 · Cited by 6,289 · see citing works
(1990) · PsycEXTRA Dataset · doi:10.1037/e530902004-001 · Cited by 3,690 · see citing works
A dark side of the American dream: Correlates of financial success as a central life aspiration
Kasser, T., & Ryan, R. M. (1993) · Journal of Personality and Social Psychology · doi:10.1037/0022-3514.65.2.410 · Cited by 2,298 · see citing works
The Psychology of Religion and Coping
Mcfadden, S., & Pargament, K. (1997) · Journal for the Scientific Study of Religion · doi:10.2307/1387534 · Cited by 1,597 · see citing works
Religious Involvement and Subjective Well-Being
Ellison, C. G. (1991) · Journal of Health and Social Behavior · doi:10.2307/2136801 · Cited by 1,472 · see citing works
Self-citationThe Religion-Health Connection: Evidence, Theory, and Future Directions
Ellison, C. G., & Levin, J. S. (1998) · Health Education & Behavior · doi:10.1177/109019819802500603 · Cited by 1,460 · see citing works
Self-citationHOUSE, J. S., ROBBINS, C., & METZNER, H. L. (1982) · American Journal of Epidemiology · doi:10.1093/oxfordjournals.aje.a113387 · Cited by 1,381 · see citing works
(1991) · Medical Entomology and Zoology · Cited by 1,352 · see citing works
Religious involvement and U.S. adult mortality
Hummer, R. A., Rogers, R. G., Nam, C. B., & Ellison, C. G. (1999) · Demography · doi:10.2307/2648114 · Cited by 825 · see citing works
Self-citationSpirituality and Health: What We Know, What We Need to Know
George, L. K., Larson, D. B., Koenig, H. G., & McCullough, M. E. (2000) · Journal of Social and Clinical Psychology · doi:10.1521/jscp.2000.19.1.102 · Cited by 702 · see citing works
Self-citationFrequent attendance at religious services and mortality over 28 years.
Strawbridge, W. J., Cohen, R. D., Shema, S. J., & Kaplan, G. A. (1997) · American Journal of Public Health · doi:10.2105/ajph.87.6.957 · Cited by 686 · see citing works
Religiosity and remission of depression in medically ill older patients
Koenig, H. G., George, L. K., & Peterson, B. L. (1998) · American Journal of Psychiatry · doi:10.1176/ajp.155.4.536 · Cited by 658 · see citing works
Self-citationThe stress process and the social distribution of depression.
Turner, R., & Lloyd, D. A. (1999) · Journal of Health and Social Behavior · doi:10.2307/2676332 · Cited by 584 · see citing works
Religion and health: Is there an association, is it valid, and is it causal?
Levin, J. S. (1994) · Social Science & Medicine · doi:10.1016/0277-9536(94)90109-0 · Cited by 581 · see citing works
Marital status and health among the elderly
Goldman, N., Korenman, S. D., & Weinstein, R. B. (1995) · Social Science & Medicine · doi:10.1016/0277-9536(94)00281-w · Cited by 553 · see citing works
Religious coping and depression among elderly, hospitalized medically ill men
(1992) · American Journal of Psychiatry · doi:10.1176/ajp.149.12.1693 · Cited by 544 · see citing works
Oxman, T. E., Freeman, D. H., & Manheimer, E. D. (1995) · Psychosomatic Medicine · doi:10.1097/00006842-199501000-00002 · Cited by 525 · see citing works
Divine Relations, Social Relations, and Well-Being
Pollner, M. (1989) · Journal of Health and Social Behavior · doi:10.2307/2136915 · Cited by 514 · see citing works
Religious Involvement and the Health of the Elderly: Some Hypotheses and an Initial Test
Idler, E. L. (1987) · Social Forces · doi:10.1093/sf/66.1.226 · Cited by 486 · see citing works
Ryan, R. M., Rigby, S., & King, K. (1993) · Journal of Personality and Social Psychology · doi:10.1037//0022-3514.65.3.586 · Cited by 436 · see citing works
Religion's Role in Promoting Health and Reducing Risk Among American Youth
Wallace, J. M., & Forman, T. A. (1998) · Health Education & Behavior · doi:10.1177/109019819802500604 · Cited by 434 · see citing works
The Santa Clara Strength of Religious Faith Questionnaire
Plante, T. G., & Boccaccini, M. T. (1997) · Pastoral Psychology · doi:10.1007/bf02230993 · Cited by 425 · see citing works
The Stress-Buffering Role of Spiritual Support: Cross-Sectional and Prospective Investigations
Matón, K. I. (1989) · Journal for the Scientific Study of Religion · doi:10.2307/1386742 · Cited by 390 · see citing works
Religion, Disability, Depression, and the Timing of Death
Idler, E. L., & Kasl, S. V. (1992) · American Journal of Sociology · doi:10.1086/229861 · Cited by 385 · see citing works
Religious Involvement and Self-Perception among Black Americans
Ellison, C. G. (1993) · Social Forces · doi:10.1093/sf/71.4.1027 · Cited by 380 · see citing works
Self-citationReligion and mortality among the community-dwelling elderly.
Oman, D., & Reed, D. (1998) · American Journal of Public Health · doi:10.2105/ajph.88.10.1469 · Cited by 350 · see citing works
Does Religious Attendance Prolong Survival? A Six-Year Follow-Up Study of 3,968 Older Adults
Koenig, H. G., Hays, J. C., Larson, D. B., George, L. K., Cohen, H. J., McCullough, M. E., Meador, K. G., & Blazer, D. G. (1999) · The Journals of Gerontology Series A: Biological Sciences and Medical Sciences · doi:10.1093/gerona/54.7.m370 · Cited by 341 · see citing works
Self-citationReligiosity Buffers Effects of Some Stressors on Depression but Exacerbates Others
Strawbridge, W. J., Shema, S. J., Cohen, R. D., Roberts, R. E., & Kaplan, G. A. (1998) · The Journals of Gerontology Series B · doi:10.1093/geronb/53b.3.s118 · Cited by 333 · see citing works
Religion and psychological distress in a community sample
Williams, D. R., Larson, D. B., Buckler, R., Heckmann, R. C., & Pyle, C. M. (1991) · Social Science & Medicine · doi:10.1016/0277-9536(91)90040-j · Cited by 324 · see citing works
Self-citationIdler, E. L., & Kasl, S. V. (1997) · The Journals of Gerontology Series B · doi:10.1093/geronb/52b.6.s306 · Cited by 296 · see citing works
Race, religious involvement and depressive symptomatology in a southeastern U.S. community
Ellison, C. G. (1995) · Social Science & Medicine · doi:10.1016/0277-9536(94)00273-v · Cited by 285 · see citing works
Self-citationThe Relationship between Religious Activities and Blood Pressure in Older Adults
Koenig, H. G., George, L. K., Hays, J. C., Larson, D. B., Cohen, H. J., & Blazer, D. G. (1998) · The International Journal of Psychiatry in Medicine · doi:10.2190/75jm-j234-5jkn-4dqd · Cited by 284 · see citing works
Self-citationKoenig, H. G., Hays, J. C., George, L. K., Blazer, D. G., Larson, D. B., & Landerman, L. R. (1997) · PubMed · Cited by 279 · see citing works
Self-citationAttendance at Religious Services and Mortality in a National Sample
Musick, M. A., House, J. S., & Williams, D. R. (2004) · Journal of Health and Social Behavior · doi:10.1177/002214650404500206 · Cited by 278 · see citing works
Religion and Health among Black and White Adults: Examining Social Support and Consolation
Ferraro, K. F., & Koch, J. R. (1994) · Journal for the Scientific Study of Religion · doi:10.2307/1386495 · Cited by 269 · see citing works
Koenig, H. G., Cohen, H. J., George, L. K., Hays, J. C., Larson, D. B., & Blazer, D. G. (1997) · The International Journal of Psychiatry in Medicine · doi:10.2190/40nf-q9y2-0gg7-4wh6 · Cited by 251 · see citing works
Self-citationDoes religious observance promote health? mortality in secular vs religious kibbutzim in Israel.
Kark, J. D., Shemi, G., Friedlander, Y., Martin, O., Manor, O., & Blondheim, S. H. (1996) · American Journal of Public Health · doi:10.2105/ajph.86.3.341 · Cited by 226 · see citing works
Religiosity and Self-Esteem among Older Adults
KRAUSE, N. M. (1995) · The Journals of Gerontology Series B · doi:10.1093/geronb/50b.5.p236 · Cited by 208 · see citing works
Koenig, H. G., Hays, J. C., George, L. K., Blazer, D. G., Larson, D. B., & Landerman, L. R. (1997) · American Journal of Geriatric Psychiatry · doi:10.1097/00019442-199721520-00006 · Cited by 203 · see citing works
Self-citationMusick, M. A., Koenig, H., Hays, J., & Cohen, H. (1998) · The journals of gerontology. Series B, Psychological sciences and social sciences · doi:10.1093/geronb/53b.4.s218 · Cited by 197 · see citing works
Child Fatalities From Religion-motivated Medical Neglect
Asser, S. M., & Swan, R. (1998) · PEDIATRICS · doi:10.1542/peds.101.4.625 · Cited by 195 · see citing works
Journal of Gerontology: MEDICAL SCIENCES
(2011) · The Journals of Gerontology Series A · doi:10.1093/gerona/glr014 · Cited by 181 · see citing works
The Effects of Family Composition, Health, and Social Support Linkages on Mortality
Rogers, R. G. (1996) · Journal of Health and Social Behavior · doi:10.2307/2137260 · Cited by 154 · see citing works
Aging, Religious Doubt, and Psychological Well-Being
Krause, N., Ingersoll‐Dayton, B., Ellison, C. G., & Wulff, K. M. (1999) · The Gerontologist · doi:10.1093/geront/39.5.525 · Cited by 135 · see citing works
Self-citationPatterns of Social Affiliation as Predictors of Depressive Symptoms Among Urban Blacks
Brown, D. R., Gary, L. E., Greene, A. D., & Milburn, N. G. (1992) · Journal of Health and Social Behavior · doi:10.2307/2137354 · Cited by 126 · see citing works
Stress, Religiosity, and Psychological Well-Being among Older Blacks
Krause, N. (1992) · Journal of Aging and Health · doi:10.1177/089826439200400305 · Cited by 125 · see citing works
Phillips, R. L., Kuzma, J. W., Beeson, W. L., & Lotz, T. M. (1980) · American Journal of Epidemiology · doi:10.1093/oxfordjournals.aje.a112996 · Cited by 118 · see citing works
Predictors of Mortality among Elderly African-Americans
Bryant, S., & Rakowski, W. (1992) · Research on Aging · doi:10.1177/0164027592141003 · Cited by 117 · see citing works
The role of religious values in coping with cancer
Acklin, M. W., Brown, E. C., & Mauger, P. A. (1983) · Journal of Religion and Health · doi:10.1007/bf02279928 · Cited by 106 · see citing works
Commerford, M. C., & Reznikoff, M. (1996) · The Journal of Psychology · doi:10.1080/00223980.1996.9914986 · Cited by 78 · see citing works
The Spiritual History Scale in Four Dimensions (SHS-4)
Hays, J. C., Meador, K. G., Branch, P. S., & George, L. K. (2001) · The Gerontologist · doi:10.1093/geront/41.2.239 · Cited by 76 · see citing works
Self-citationPsychosocial factors among members of religious and secular kibbutzim.
Jd, K., Carmel, S., Sinnreich, R., Goldberger, N., & Friedlander, Y. (1996) · PubMed · Cited by 76 · see citing works
Depression and Physical Disability Outcomes in Depressed Medically Ill Hospitalized Older Adults
Koenig, H. G., & George, L. K. (1998) · American Journal of Geriatric Psychiatry · doi:10.1097/00019442-199800630-00006 · Cited by 74 · see citing works
Self-citationReligious Denomination and Depression in Older Dutch Citizens
Braam, A. W., Beekman, A. T. F., Knipscheer, C. P. M., et al. (1998) · Journal of Aging and Health · doi:10.1177/089826439801000405 · Cited by 70 · see citing works
Religion and the Survival of 1010 Hospitalized Veterans
Koenig, H. G., Larson, D. B., Hays, J. C., McCullough, M. E., George, L. K., Branch, P. S., Meader, K. G., & Kuchibhatla, M. N. (1998) · Journal of Religion and Health · doi:10.1023/a:1022904915837 · Cited by 63 · see citing works
Self-citationComparative Longevity in a College Cohort of Christian Scientists
Simpson, W. F. (1989) · JAMA · doi:10.1001/jama.1989.03430120111031 · Cited by 62 · see citing works
Comparative longevity in a college cohort of Christian Scientists
Simpson, W. F. (1989) · JAMA · doi:10.1001/jama.262.12.1657 · Cited by 60 · see citing works
Religious Activity, Alcohol Use, and Depression in a Sample of Elderly Baptists
Musick, M. A., Blazer, D. G., & Hays, J. C. (2000) · Research on Aging · doi:10.1177/0164027500222001 · Cited by 57 · see citing works
Depression and Physical Disability Outcomes in Depressed Medically Ill Hospitalized Older Adults
Koenig, H. G., & George, L. K. (1998) · American Journal of Geriatric Psychiatry · doi:10.1097/00019442-199808000-00006 · Cited by 41 · see citing works
Self-citationBehavioral Factors Explaining the Low Risk for Cervical Carcinoma in Utah Mormon Women
Gardner, J. W., Sanborn, J. S., & Slattery, M. L. (1995) · Epidemiology · doi:10.1097/00001648-199503000-00019 · Cited by 30 · see citing works
Flagged first, then by citations
Cited by
Sorted by citations
Fiske, A., Wetherell, J. L., & Gatz, M. (2009) · Annual Review of Clinical Psychology · doi:10.1146/annurev.clinpsy.032408.153621 · Cited by 2,353 · see citing works
Hill, P. C., & Pargament, K. I. (2003) · American Psychologist · doi:10.1037/0003-066x.58.1.64 · Cited by 1,948 · see citing works
Spirituality, religion, and health: An emerging research field.
Miller, W. R., & Thoresen, C. E. (2003) · American Psychologist · doi:10.1037/0003-066x.58.1.24 · Cited by 1,437 · see citing works
Religion and spirituality: Linkages to physical health.
Powell, L. H., Shahabi, L., & Thoresen, C. E. (2003) · American Psychologist · doi:10.1037/0003-066x.58.1.36 · Cited by 1,093 · see citing works
Pargament, K. I., Koenig, H. G., Tarakeshwar, N., & Hahn, J. (2004) · Journal of Health Psychology · doi:10.1177/1359105304045366 · Cited by 912 · see citing works
Religiousness and mental health: a review
Moreira-Almeida, A., Lotufo Neto, F., & Koenig, H. G. (2006) · Revista Brasileira de Psiquiatria · doi:10.1590/s1516-44462006005000006 · Cited by 835 · see citing works
Fincher, C. L., & Thornhill, R. (2012) · Behavioral and Brain Sciences · doi:10.1017/s0140525x11000021 · Cited by 526 · see citing works
Rew, L., & Wong, Y. J. (2006) · Journal of Adolescent Health · doi:10.1016/j.jadohealth.2005.02.004 · Cited by 380 · see citing works
Wink, P., & Scott, J. (2005) · The Journals of Gerontology Series B: Psychological Sciences and Social Sciences · doi:10.1093/geronb/60.4.p207 · Cited by 234 · see citing works
Religious attendance and the health behaviors of Texas adults
Hill, T. D., Burdette, A. M., Ellison, C. G., & Musick, M. A. (2006) · Preventive Medicine · doi:10.1016/j.ypmed.2005.12.005 · Cited by 226 · see citing works
Self-citationReligious Attendance and Mortality: An 8-Year Follow-Up of Older Mexican Americans
Hill, T. D., Angel, J. L., Ellison, C. G., & Angel, R. J. (2005) · The Journals of Gerontology Series B: Psychological Sciences and Social Sciences · doi:10.1093/geronb/60.2.s102 · Cited by 202 · see citing works
Self-citationReligious Participation, Interleukin-6, and Mortality in Older Adults.
Lutgendorf, S. K., Russell, D., Ullrich, P., Harris, T. B., & Wallace, R. (2004) · Health Psychology · doi:10.1037/0278-6133.23.5.465 · Cited by 184 · see citing works
Dew, R. E., Daniel, S. S., Goldston, D. B., McCall, W. V., Kuchibhatla, M., Schleifer, C., Triplett, M. F., & Koenig, H. G. (2010) · Journal of Affective Disorders · doi:10.1016/j.jad.2009.04.029 · Cited by 159 · see citing works
Religious attendance and mortality: Implications for the black-white mortality crossover
Dupre, M. E., Franzese, A. T., & Parrado, E. A. (2006) · Demography · doi:10.1353/dem.2006.0004 · Cited by 142 · see citing works
Does compassion mediate the intrinsic religion-health relationship?
Steffen, P. R., & Masters, K. S. (2005) · Annals of Behavioral Medicine · doi:10.1207/s15324796abm3003_6 · Cited by 135 · see citing works
A prospective study of church attendance and health over the lifespan.
Koenig, L. B., & Vaillant, G. E. (2009) · Health Psychology · doi:10.1037/a0012984 · Cited by 127 · see citing works
Ellison, C. G., & Flannelly, K. J. (2009) · Journal of Nervous & Mental Disease · doi:10.1097/nmd.0b013e3181b08f45 · Cited by 125 · see citing works
Self-citationAdvancing our understanding of religion and spirituality in the context of behavioral medicine
Park, C. L., Masters, K. S., Salsman, J. M., Wachholtz, A., Clements, A. D., Salmoirago-Blotcher, E., Trevino, K., & Wischenka, D. M. (2017) · Journal of Behavioral Medicine · doi:10.1007/s10865-016-9755-5 · Cited by 119 · see citing works
Dimensions of religious involvement and leukocyte telomere length
Hill, T. D., Ellison, C. G., Burdette, A. M., Taylor, J., & Friedman, K. L. (2016) · Social Science & Medicine · doi:10.1016/j.socscimed.2016.04.032 · Cited by 116 · see citing works
Self-citationReligious orientation, aging, and blood pressure reactivity to interpersonal and cognitive stressors
Masters, K. S., Hill, R. D., Kircher, J. C., Benson, T. L. L., & Fallon, J. A. (2004) · Annals of Behavioral Medicine · doi:10.1207/s15324796abm2803_5 · Cited by 117 · see citing works
Ai, A. L., Peterson, C., Bolling, S. F., & Rodgers, W. (2006) · Journal of Psychosomatic Research · doi:10.1016/j.jpsychores.2005.06.082 · Cited by 103 · see citing works
Ai, A. L., Wink, P., Tice, T. N., Bolling, S. F., & Shearer, M. (2009) · Journal of Behavioral Medicine · doi:10.1007/s10865-009-9228-1 · Cited by 95 · see citing works
Religiosity and Health: A Holistic Biopsychosocial Perspective
Page, R. L., Peltzer, J. N., Burdette, A. M., & Hill, T. D. (2020) · Journal of Holistic Nursing · doi:10.1177/0898010118783502 · Cited by 91 · see citing works
Religiousness and Longitudinal Trajectories in Elders' Functional Status
Park, N. S., Klemmack, D. L., Roff, L. L., Parker, M. W., Koenig, H. G., Sawyer, P., & Allman, R. M. (2008) · Research on Aging · doi:10.1177/0164027507313001 · Cited by 77 · see citing works
Religiousness and spirituality in fibromyalgia and chronic pain patients
Moreira-Almeida, A., & Koenig, H. G. (2008) · Current Pain and Headache Reports · doi:10.1007/s11916-008-0055-9 · Cited by 61 · see citing works
Enduring as Lived Experience: Exploring the Essence of Spiritual Resilience for Women in Late Life
Manning, L. K. (2014) · Journal of Religion and Health · doi:10.1007/s10943-012-9633-6 · Cited by 50 · see citing works
Religiousness and Treatment Adherence in Congestive Heart Failure Patients
Park, C. L., Moehl, B., Fenster, J. R., Suresh, D. P., & Bliss, D. (2008) · Journal of Religion, Spirituality & Aging · doi:10.1080/15528030802232270 · Cited by 33 · see citing works
- Authors
- George, L. K., Ellison, C. G., & Larson, D. B.
- Affiliations
- Duke University (US)
- The University of Texas at Austin (US)
- Venue
- Psychological Inquiry
- Publisher
- Informa UK Limited
- Published
- 2002-07
- Volume
- 13
- Issue
- 3
- Pages
- 190-200
- ISSN
- 1047-840X (ISSN-L)
- 1532-7965
- OpenAlex
- W1972423849
- Cited by
- 847
- References
- 61
- Citations by year
- 2026: 15 · 2025: 20 · 2024: 24 · 2023: 25 · 2022: 31 · 2021: 42 · 2020: 32 · 2019: 38 · 2018: 42 · 2017: 30 · 2016: 38 · 2015: 28 · 2014: 67 · 2013: 61 · 2012: 46
- FWCI
- 21.70
- Type
- journal article
- Language
- en
- Open access
- closed
- Locations
- Psychological Inquiry (publishedVersion)
- Topics
- Social Sciences › Health › Religion, Spirituality, and Psychology
- Social Sciences › Sociology and Political Science › Religion and Society Interactions
- Health Sciences › Health Professions › General Health Professions › Health, psychology, and well-being
- Keywords
- religious involvement, religion and health, psychosocial mechanisms, health practices, social support, self-esteem, self-efficacy, sense of coherence, longevity, physical health, mental health
About these checks
Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.
Statistics and arithmetic are recomputed, not judged.
Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.
What counts as a claim ›How we measure confidence ›How we check this ›
Are you an author, or do you see a problem with this page? Request a review