PhD advisors can be abusive. Your career is in their hands. They can use their power to coerce you beyond an ethical limit without them understanding how abusive they are being. The emotional strain can be intense. I’ve detailed some of the problems I had with my advisor in an answer to the question What are some PhD horror stories? I was too determined to succeed to let it stop me. A slight difference in my attitude could have had me leaving the program.
The emotional stress of a PhD program cannot be understood by people who have not gone through it. When you are feeling low, it is common to look for emotional support from your family and friends. If they haven’t had the experience themselves, they can make things worse. In my case, talking to my parents once about different issues I was having with my PhD advisor just added to the stress. Since they couldn’t understand the abuse, they presumed I must have done something wrong. Reaching out to your loved ones for emotional support and getting condemnation can be emotionally brutal.