In an interview with the Press And Journal, Ms Forbes – who was Scottish finance secretary under Nicola Sturgeon before vying to replace her in the contest earlier this year – laid bare her struggles with mental health issues after the birth of her daughter Naomi last year.
Following what was a difficult birth, during which the MSP says she started to lose blood and became “completely white and unresponsive”, she was hit with a “sense of huge relief” before Naomi was taken away to a specialist unit.
She told how when she returned home from hospital to Dingwall, in the Highlands, with husband Ali and Naomi, she experienced a downturn in her mental health.
“I have never, over my lifetime, had any particular challenges with mental health,” Ms Forbes told the paper.
“We all have highs and lows and periods of difficulty, sadness, grief or anxiety, but this was something totally different.
“To start with, I had insomnia, complete insomnia. I couldn’t sleep a wink. I couldn’t nap. I went days on end being unable to sleep. That was accompanied by quite extreme levels of terror.
“Terror when I was awake and during the day. Fear that something awful was going to happen. I couldn’t really comfortably be anywhere alone in the house for fear.
“But then at night total night terrors of seeing very visibly somebody causing harm to me or to the baby.
“Then just being wracked by guilt, anxiety, intense sadness, and feeling extraordinarily vulnerable and like I’d caused other people huge difficulty; that I’d wrecked their lives.”
Ms Forbes also said she was scared of bathing her newborn, for fear “I would cause her harm”.
After speaking to her midwife, Ms Forbes was diagnosed with post-natal depression and received support from her husband and wider family.
The MSP said she has been “absolutely stunned” about the lack of understanding over the condition, adding that there should be improved training for midwives on mental health.