Rumer Willis' Instagram photo exposes the dark truth about Hollywood kids.

Rumer Willis was raised in Idaho, but is well and truly a child of Hollywood. Her mother, Demi Moore, hired a cameraman to capture her birth on film; a birth that happened while her father, Bruce Willis, was shooting the movie In Country.

The 28-year-old is now even an actress herself, with a recurring role in the HBO drama Empire and credits on Broadway. But that’s not to say her life has been all glitz and applause.

This week Willis publicly acknowledged her private struggle with addiction.

“I will be the first one to say I’m not perfect and I mess up sometimes and every once in a while I get it right but I wanted to share this because I am really proud of myself,” she wrote on Instagram.

“Yesterday I celebrated 6 Months of Sobriety. It’s not something I planned on but after the long journey of getting here I can honestly say I have never been more proud of myself in my entire life. Thank you all for the love and support and remember to be gentle with yourself.”

I will be the first one to say I’m not perfect and I mess up sometimes and every once in a while I get it right but I wanted to share this because I am really proud of myself. Yesterday I celebrated 6 Months of Sobriety. It’s not something I planned on but after the long journey of getting here I can honestly say I have never been more proud of myself in my entire life. Thank you all for the love and support and remember to be gentle with yourself ????

A post shared by Rumer Willis (@ruelarue) on Jul 1, 2017 at 11:08am PDT

Her younger sister, Tallulah, has had similar struggles in the past. The now 23-year-old spoke 2015 about a period in which drug use and depression collided in a hugely destructive way.

“I was so removed from my body and from my mind that it was like I was living in a cardboard replica of what life should be,” she wrote for Teen Vogue at the time. “Not even so much because I was doing drugs, but because I was so sad and so unhappy.”

It had begun early.

“Because I spent my early childhood on our ranch in Idaho, I hadn’t processed the full extent of my family’s fame until I moved to Los Angeles and started third grade,” she wrote. “Then, suddenly, I didn’t think I deserved what I had grown up with, and I remember thinking I couldn’t have problems, so I kept everything bottled up inside.”

After 45 days in rehab, Willis acknowledged that she still has problems; “[But] I can say that I’m getting to that place where I’m starting to feel OK with myself, bit by bit.”

Actor Samuel Johnson opens up about his drinking. Post continues below.

These women are among a company of Hollywood children to have experienced problems with addiction or substance abuse. There are the well documented cases – the Nicole Richies, the Kelly and Jack Osbournes – whose drug issues have played out dramatically and publicly.

But there are also those who have struggled largely in private, until they shone the spotlight on themselves.

Like Bon Jovi’s daughter, Stephanie Bongiovi, who was hospitalised after overdosing on heroin in her New York college dorm room in 2011.

Like Farrah Fawecett’s son, Redmond O’Neal, who was sentenced to one year in prison and an intense inpatient rehab program for substance abuse after being caught with heroin during a 2011 traffic stop.

Like Michael Douglas' son, Cameron, who was jailed in 2010 after he was caught selling heroin in a New York hotel room. Himself the son of legendary actor Kirk Douglas, Michael pleaded with the court to show leniency to his son, writing, "I have some idea of the pressure of finding your own identity with a famous father. I'm not sure I can comprehend it with two generations to deal with."

And like like Tom Hanks and Rita Wilson's son, Chet Hanks, who checked into rehab for cocaine abuse in 2015 and revealed he'd been using various drugs since the age of 16.

“At the end of the day all the stupid s--- I was doing that's not who I am, that's not who I want to be,” the now 26-year-old said in an Instagram video. “It's been a long journey for me discovering who I am because of all the pressures that I've dealt with in my life, being the son of my dad and everything and just trying to find where I fit in."