Environmental Factors Impact Psoriasis Severity
In a comprehensive review, researchers aimed to explore seasonality, environmental factors, and the genetic and epigenetic mechanisms of patients living with psoriasis vulgaris.
Environmental factors, like sun exposure, humidity, air pollution, and circadian rhythm, were key contributors to increasing psoriasis activity and severity, according to a study published in the International Journal of Molecular Science.1
“Psoriasis vulgaris (PsV) is a chronic systemic inflammatory disease that significantly impacts patients’ quality of life,” wrote authors of the study. “Depending on the geographic region, PsV affects from 0.27% to 11.4% of the worldwide population. Ten to 40% of psoriatic patients are affected with psoriatic arthritis (PsA).”
Psoriasis in many of its forms can be significantly debilitating on a patients’ quality of life and overall health. Due to the inflammatory symptoms patients with psoriasis often encounter, they are also put at risk of developing comorbidities including cardiovascular disorders, metabolic syndrome, nonalcoholic fatty liver disease, and inflammatory bowel disease.1
The researchers’ goal was to further understand the seasonality of PsV by exploring its molecular mechanisms and how they relate to environmental factors. | image credit: Africa Studio / stock.adobe.com
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While psoriasis can serve as a blanket term and even turn into arthritis later in life, PsV is a bit different. PsV is the most common form of psoriasis comprising around 90% of all cases.2 On the surface, psoriasis impacts 125 million people worldwide and over 8 million Americans.3 However, according to current study authors, PsV impacts more than just an individual’s personal health.
“Due to visible skin lesions and a proinflammatory background, psoriasis is associated with a lower quality of life and psychiatric disorders such as depression and anxiety,” they continued.1 “Patients affected by PsV experience reduced levels of employment and income. Beyond geographic differences, psoriasis is affected by environmental factors and presents different seasonal patterns.”
Given their current understanding of both psoriasis and PsV, also known as plaque psoriasis,4 researchers’ goal was to further understand the seasonality of PsV.1 They did so by exploring molecular mechanisms in PsV and assessing how they impact treatment strategies and patient adherence.
In their review, researchers explored various databases for a slew of keywords and how they were related to PsV. Some of those keywords included “environmental factors,” “genetics,” “epigenetics,” “solar radiation,” “humidity,” “air pollution,” and more. After considering studies only up to March 10, 2024, “the remaining articles’ abstracts were read, and the relevant articles relating to seasonality and environmental factors [were] read in full and included in the analysis.”
After introducing PsV and its molecular background, researchers then explored the environmental factors identified in their review. These factors included sunlight, humidity, air pollution, and circadian rhythm.
“The significance of sunlight and its impact on psoriasis is well established. Phototherapy is one of the most common treatment options for children and adults. Exposure to solar radiation in skin influences several epidermis functions due to apoptosis, DNA damage responses and cell cycle control, innate and acquired immune regulation and inflammation, redox response and angiogenesis, circadian rhythmicity, and keratinocyte differentiation,” they wrote.1
In their key findings related to humidity and PsV, researchers identified a significant association between psoriasis and water loss—or decreased subcutaneous water content. For PsV specifically, they also discovered reduced water content in the epidermis reported to have similar features when compared with PsV plaques or lesions.
“Particulate matter and nitrogen dioxide cause oxidative damage to the epithelial cells by production of volatile organic compounds,” continued the authors.1
Air pollution’s ability to cause oxidative damage can be a concern for patients living with PsV. In the researchers’ findings, air pollution was reported in causing psoriasis flare-ups because of seasonal patterns from indoor heating and a decrease in UV exposure during the winter months.
They also mentioned how cigarette smoke can exacerbate psoriasis, while PsV patients are more prone to pulmonary diseases such as asthma and obstructive sleep apnea.
A previous study explored in the review “reported a higher risk of incidence of psoriasis and psoriatic comorbidities in rotating night shift health care workers. This phenomenon can be explained by lower exposure to sunlight, decreased vitamin D levels, reduced production of melatonin, or a tendency to behavioral disruptions, but also by the circadian rhythm’s disturbance,” according to the study authors.1
With overlap among some of the aforementioned environmental factors, there are a variety of seasonal changes that patients with psoriasis, as well as their providers, should be aware of. While it’s now better understood that common environmental factors impact psoriasis outcomes, future research will further flesh out the seasonality of psoriasis and how the disease should be treated going forward.
“Psoriasis activity and severity are affected by epigenetic and environmental factors such as sun exposure, humidity, air pollution, and circadian rhythm,” concluded the authors.1 “The seasonality of psoriasis may be related to a different expression of genes with a more proinflammatory immune system and various environmental changes observed as the evolutionary adaptation of humans to more difficult environmental conditions during autumn, winter, and early spring in temperate and subpolar climate regions.”
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References
1. Niedźwiedź M, Skibińska M, Ciążyńska M, et al. Psoriasis and seasonality: exploring the genetic and epigenetic interactions. Int J Mol Sci. 2024;25(21):11670. https://doi.org/10.3390/ijms252111670
2. Sarac G, Koca TT, Baglan T. A brief summary of clinical types of psoriasis. North Clin Istanb. 2016 Jun 14;3(1):79-82. doi: 10.14744/nci.2016.16023.
3. Psoriasis statistics. National Psoriasis Foundation. December 21, 2022. Accessed April 8, 2025. https://www.psoriasis.org/psoriasis-statistics
4. Fu Y, Li X, Chen Y, et al. Association of ERAP1 gene polymorphisms with the susceptibility to psoriasis vulgaris. J Med. 2018;97(41):e12828. https://doi.org/10.1097/md.0000000000012828
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