Alanis Morissette Say She Had 'Harrowing' Invasive Thoughts During Postpartum Depression

Alanis Morissette says you oughta know postpartum depression can seriously screw with your mental state ... admitting she had scary invasive thoughts during her own struggle.

The singer-songwriter joined Alex Cooper on her "Call Her Daddy" podcast to discuss dealing with the disorder ... telling Alex her postpartum became worse and worse after each pregnancy. She has three children.

Alanis says she essentially became another person ... plagued by super "harrowing" invasive thoughts -- as well as anxiety, depression and rage.

She says she was so confused about what was happening to her the first time she had to deal with postpartum ... and, when she went to speak to mental health professionals, she says their advice wasn't helpful.

On top of it all, Alanis says she was still touring and dealing with all the issues that arise during that process ... which didn't help her mental state either.

Worth noting ... this episode came out Wednesday -- amid the hotly contested Lindsay Clancy trial. As we've reported, Lindsay admitted to killing her three children, but her lawyers say she was not in control of her actions during her postpartum psychosis.

Lindsay's trial ended with a hung jury ... and many online are attacking her for allegedly using the postpartum defense.