Crying won't cause blocked tear duct. Tear is produced by glands located above each eye. It flows down evenly through the surface of eyeball and then drains into puncta in corner of eyelids. Then tear just travels down a duct before emptying into nose. The block could happen at any point of this drainage way. Once you got it, you might have watering eyes, which at the same time increases the risk of infection or inflammation. Normally, you can get it for two possibilities. You might be born with it, which means it is congenital defect. Or you might develop it because of trauma to eyes, eye infections or inflammations, abnormal development of skull and face, and some changes related to aging. For me, I think crying is good to health. First of all tears are precious to eyes. They can kill bacteria up to 90%-95% in eyes. They are very important lubricant so that we can turn eyeballs without gritty and uncomfortable feelings. Tears can help wash foreign subjects out of eyes too. Meanwhile crying could help relieve depression and your emotion. There is no need to hold it back. After a good crying, you will feel much better and more relaxed. After all, I am a girl who likes crying. If I meet something bad, anything makes me depressed and sad, it is easy to get me cry. But after crying, I found myself in a better mood, and get move on.
Blocked tear ducts could be inborn for new babies. However, as to adults, it could be resulted from chronic dacryocystitis, which could lead to blocked tear ducts, and basically crying would not cause that. So, once you find your eyes abnormal, you should try to take an eye exam and get your tear ducts fixed, or take an eye surgery to fix the problem.
Well, crying can not lead to the blocked tear duct. So you do not need to worry about it. In common, the ducts that drain tears from your eyes can become blocked due to aging, infection, inflammation, injury, tumour, or cyst. Blocked ducts can also increase risk of eye infection and inflammation. So just pay more attention to it.