Rachel Platten has described her “incredibly painful battle” with her mental health after the birth of her baby.

The American singer marked six months since her daughter was born with a long post on Instagram detailing her struggles during the postpartum period and how she came through the difficult times.

The 40-year-old, who shot to fame with her ballad Fight Song in 2015, which then became Hillary Clinton’s presidential campaign anthem in 2016, posted a picture of her holding her daughter and smiling, with a caption beginning “Sophie is 6 months old today. Wow.”

It continues: “I feel so proud of myself, I got through an incredibly painful battle with my mental health, long days that felt impossible and tears that wouldn’t stop coming and nights that felt never ending when my poor scared body wouldn’t let me sleep.”

She wrote that she tried “every tool possible”, including things she was “scared of”, and that she now feels “consistent joy, ease, power and real hope again”.

She added that she now knows her strength and worth and that she welcomes her “insecurities and weaknesses and all my glorious sunny parts too”, and that this gives her power.

Sophie Jo is Platten’s second child with husband Kevin Lazan. They also have a three-year-old daughter, Violet Skye.

Her post continues with a message of hope to those who also struggle with mental health.

It reads: “I just want to reach a hand back into the darkness if any of you reading this are still there. I promise, it’s possible for you to feel joy again.

“I’m here as an example that you can do this. You can be your own hero and you can learn to love all of you and I believe in you.”

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Rachel Platten wrote about her mental health struggles in an Instagram post (Peter Byrne/PA)

It ends with an uplifting quote given to the musician by her aunt after she lost her husband of 50 years.

The quote reads: “Rachel, no one is going to come save you. Be your own hero. Do one brave thing today. Do one more tomorrow. Win the day. You can do this.”

Platten ends the caption with: “She was teaching me how to climb out of hell. So I’m passing it on, you can do this. Win the day. I love you all.

“Happy 6 months my angel Sophie jo.”