A hairdresser has helped a teen battling depression who felt “so worthless she couldn’t even brush her hair”.

The 16-year-old from Waterloo in Iowa, US approached Kayley Olsson to cut all her hair off because the teen couldn’t “deal with the pain of combing it out”, according to the stylist’s Facebook post.

“I had a 16-year [old] girl come in who has been dealing with severe depression for a few years now,” Ms Olsson’s Facebook post read.

“She got to the point where she felt so down and so worthless she couldn’t even brush her hair.”

It took 13 hours to detangle the girl’s hair for her school photos. Photo: Facebook: Kayley Olsson

The teenager starts back at school in a couple of weeks and was attempting to fix her hair for school photos.

Ms Olsson said the story broke her heart and she refused to cut the girl’s hair off, instead spending 13 hours over two days with another hairdresser detangling and styling the girl’s hair.

“I will actually smile for my school pictures today, you made me feel like me again,” the girl told Ms Olsson.

The process was captured and posted on Facebook, but Ms Olsson was careful not to reveal the teenager’s identity.

The hairdresser hoped the story would urge parents to take their children’s mental health seriously.

“Don’t just push your kids off and tell them to get over something they legitimately can’t,” she said.

The post sparked a flood of comments from people who have also experienced the debilitating effects of mental illness.

“I can honestly relate to this. I get into such deep ruts, I stop washing my hair and when I take showers I just ignore it because I don’t have the mentality or strength to wash it,” Makayla Butler wrote.

“This touched me so much as my daughter has depression with anxiety and doesn’t take care of herself like she should. If only she could see her worth through the eyes of those who love her most,” Jody Holland wrote.