i heard that you can get a lot of ridging if you are a smoker due to lowered blood oxygen levels. i dont smoke and have a few on my thumb nails, but they’re notoriously bad for their oxygen perfusion, have a lot of problems with it at the moment!
i also get massive horizontal ridges on my toe nails due to nutrient deficiencies (get them when i cant eat for a few days/weeks) and eventually when the ridge reaches halfway along my toes (from bed to tip) the nail snaps off. happened so often since i was a kid that i’ve lost count. i can use the ridges like a medical diary to tell me roughly how long ago my tum last went on strike, its actually very useful!. as i dont have many vertical ridges i’m not sure those are related to nutrient deficiencies….. but other changes (like flaking, spotting etc ) are likely to be nutritional…..
although i could be talking (writing?) rubbish as it’s nearly 3 am and i should have gone to bed hours ago but got sucked into this new (to me) forum. told myself to look at it in the morning but just couldnt wait!