Month: October 2021

It’s an old line: everyone complains about the weather but no one is doing anything about it.

But if you’re a person with bad allergies or asthma, stormy weather can be more than an annoyance; it can be a serious threat to your health. “Thunderstorm asthma” was first reported in the 1980s in England and Australia, and cases continue to crop up. Just after severe thunderstorms passed through Melbourne, Australia in 2016, more than 9,000 people sought urgent medical care for asthma during one notable event. Medical facilities were overwhelmed and at least eight people died. That’s unusual, but if you do have asthma — or seasonal allergies, as it turns out — understanding this trigger can help you stay well.

What is thunderstorm asthma?

The term describes an attack of asthma that starts or worsens after a thunderstorm. It can occur in anyone with asthma, but it most often affects people with seasonal allergic rhinitis, which many people know as hay fever or allergies. Heralded by a runny nose, sneezing, and itchy eyes, seasonal allergies are often worst in the spring, summer, or early fall.

Rain tends to lower pollen counts by cleansing the air, and many people find that rainy weather tends to reduce asthma symptoms triggered by allergies. But thunderstorms can make asthma worse because of a unique sequence of events:

• Cold downdrafts concentrate air particles, such as pollen and mold
• These air particles are swept up into clouds where humidity is high
• In the clouds, wind, humidity, and lightning break up the particles to a size that can readily enter the nose, sinuses, and lungs
• Wind gusts concentrate these small particles so large amounts can be inhaled.

What raises risk for experiencing thunderstorm asthma?

According to a new study in the Journal of Allergy and Clinical Immunology, a whopping 144 out of 228 people with seasonal allergies reported experiencing thunderstorm asthma — that’s 65%! And many of the asthma attacks set off by thunderstorms weren’t mild. Nearly half of people who had an attack sought emergency hospital treatment.

Among people with seasonal allergies, risk factors for experiencing thunderstorm asthma include having

• poorly controlled asthma symptoms (assessed by a standard asthma questionnaire)
• a low score on a rapid exhalation test (a common breathing test for asthma)
• higher levels of a certain antibody (ryegrass pollen-specific IgE)
• higher numbers of certain blood cells (eosinophils, which tend to increase when people have allergic conditions)
• higher levels of exhaled nitric oxide (one measure of lung inflammation among people with asthma).

Not everyone with these risk factors will develop thunderstorm asthma. And even among those who do, asthma attacks won’t necessarily occur with every storm. But it may be useful to know if you’re among those at risk, especially if you live in an area where thunderstorms are common.

The bottom line

Thunderstorm asthma may seem like more of a curiosity than a serious threat to public health. But when it affects a large population area, emergency rooms can become overwhelmed, as happened during the 2016 Melbourne event. A better understanding of when these events are expected could lead to advanced warning systems, enhanced emergency room preparedness, and even preventive treatment.

In the US, 25 million people have asthma and more than 20 million have seasonal allergies. Odds are good that millions have both, which puts large numbers of people at risk for developing thunderstorm asthma.

If you’re among them, the weather forecast may be much more than just a guide on what to wear or whether to bring an umbrella. Knowing thunderstorms are headed your way may serve as an advance warning to double check that you are taking your asthma medicines properly, have a supply of rescue medicine handy, or simply plan to stay indoors until the storm has passed.

About the Author

Robert H. Shmerling, MD, Senior Faculty Editor, Harvard Health Publishing

Dr. Robert H. Shmerling is the former clinical chief of the division of rheumatology at Beth Israel Deaconess Medical Center (BIDMC), and is a current member of the corresponding faculty in medicine at Harvard Medical School. … See Full Bio View all posts by Robert H. Shmerling, MD

As of June 2022, 37 US states have passed medical cannabis laws and 19 states have legalized recreational cannabis. Cannabis has proven beneficial for a range of conditions such as childhood seizure disorders, nausea, vomiting, and loss of appetite in people with HIV/AIDs.

In the meantime, a new generation of cannabis products has exploded onto the scene, driven by marketing that fuels a multibillion-dollar industry. The average content of THC (tetra-9-tetrahydrocannabinol, the psychoactive and potentially addictive chemical in cannabis) in smoked whole-plant products has risen from 1% to 4% in the 1970s to 15% to 30% from today’s cannabis dispensaries. Edibles and vapes may contain even higher concentrations of THC.

While public perception that cannabis is a harmless substance is growing, the long-term benefits and risks of cannabis use remain unclear. However, one consistent pattern of research has emerged: heavy long-term cannabis use can impact midlife cognition.

New research on cannabis use and cognition in midlife

Recent research published in The American Journal of Psychiatry closely followed nearly 1,000 individuals in New Zealand from age 3 to age 45 to understand the impact of cannabis use on brain function. The research team discovered that individuals who used cannabis long-term (for several years or more) and heavily (at least weekly, though a majority in their study used more than four times a week) exhibited impairments across several domains of cognition.

Long-term cannabis users’ IQs declined by 5.5 points on average from childhood, and there were deficits in learning and processing speed compared to people that did not use cannabis. The more frequently an individual used cannabis, the greater the resulting cognitive impairment, suggesting a potential causative link.

The study also found that people who knew these long-term cannabis users well observed that they had developed memory and attention problems. The above findings persisted even when the study authors controlled for factors such as dependence on other drugs, childhood socioeconomic status, or baseline childhood intelligence.

The impact of cannabis on cognitive impairment was greater than that of alcohol or tobacco use. Long-term cannabis users also had smaller hippocampi (the region of the brain responsible for learning and memory). Interestingly, individuals who used cannabis less than once a week with no history of developing dependence did not have cannabis-related cognitive deficits. This suggests there is a range of recreational use that may not lead to long-term cognitive issues.

More studies are needed on cannabis use and brain health

The new research is just one of several studies suggesting there is a link between long-term heavy cannabis use and cognition. Still, future studies are needed to establish causation and explore how long-term cannabis use might impact the risk of developing dementia, since midlife cognitive impairment is associated with higher rates of dementia.

What should you do if you experience cognitive effects of cannabis?

Some people who consume cannabis long-term may develop brain fog, lowered motivation, difficulty with learning, or difficulty with attention. Symptoms are typically reversible, though using products with higher THC content may increase risk of developing cognitive symptoms.

Consider the following if you are experiencing cannabis-related cognitive symptoms:

• Try a slow taper. Gradually decrease the potency (THC content) of cannabis you use or how frequently you use it over several weeks, especially if you have a history of cannabis withdrawal.
• Work with your doctor. Be open with your doctor about your cognitive symptoms, as other medical or psychiatric factors may be at play. Your doctor can also help you navigate a cannabis taper safely, and potentially more comfortably, using other supportive means. Unfortunately, most patients are not comfortable talking with their doctors about cannabis use.
• Give it time. It may take up to a month before you experience improvements after reducing your dose, as cannabis can remain in the body for two to four weeks.
• Try objective cognitive tracking. Using an app or objective test such as the mini-mental status exam to track your brain function may be more accurate than self-observation. Your mental health provider may be able to assist with administering intermittent cognitive assessments.
• Consider alternative strategies. Brain function is not static, like eye color or the number of toes on our feet. Aerobic exercise and engaging in mindfulness, meditation, and psychotherapy may improve long-term cognition.

Cannabis is an exciting yet controversial topic that has drawn both hype and skepticism. It is important for individuals and healthcare professionals to place emphasis on research studies and not on speculation or personal stories. Emerging studies suggesting the connection between long-term heavy use of cannabis and neurocognition should raise concern for policymakers, providers, and patients.

About the Authors

Kevin Hill, MD, MHS, Contributor

Dr. Kevin Hill is director of addiction psychiatry at Beth Israel Deaconess Medical Center, and an associate professor of psychiatry at Harvard Medical School. He earned a master’s in health science at the Robert Wood Johnson … See Full Bio View all posts by Kevin Hill, MD, MHS

Michael Hsu, MD, Guest Contributor

Dr. Michael Hsu is a resident psychiatrist and is currently the chief resident of outpatient psychiatry at Brigham and Women's Hospital, a teaching hospital of Harvard Medical School. After graduating from the University of Pennsylvania with … See Full Bio View all posts by Michael Hsu, MD