Bad effects will only happen if a person will get addicted to gambling and will forget that gambling will do no good if abused. Do gambling only in a spare time and with a spare money to avoid bigger losses.
Bad effects will not only happen to those who are addicted but it may happen for everyone. Lets say, there is someone who are just started to gamble because he thinks that he will win much money then he decided to spend all what he have but unluckily he lose it all. He is not addicted but he get the bad effects.
Obviously addicted gamblers have bigger chance to face the bad effects but gambling is still gambling, its good and bad effect may occur anytime anywhere to anyone.