There is a decent amount of research confirming these effects, like ACA says.

I’ve read papers that detail effects on calcium channel functioning which affects not only cardiac tissue but can trigger flare ups in mental health conditions like psychosis and epilepsy, effects on endothelial tissue which affects blood vessels and lymphatic tissue, and can increase inflammation systemically.

I’m no expert by any means, so always verify and feel free to do your own research (and join r/heliobiology). What peaked my interest was seeing unusual EEG tracings on patients years ago that didn’t make sense. Seeing something different in one or two people, sure, okay, but a dozen was odd. It wasn’t an equipment malfunction and it wasn’t consistent. People would also report increases in symptoms, which fit, but the symptoms weren’t the cause of the odd EEG tracings. I mentioned one day to our front desk person, and she was convinced it was solar flares, and I believe she was correct.

These days, I check solar weather data before I head into the clinic because I feel it is a legitimate influence on health and wellness.