The tragic lives of some of the biggest stars of '70s sitcoms revealed

Before he was a huge Hollywood star, Robin Williams rose to fame as a comedian before starring on Mork & Mindy in the late '70s and early '80s, the same time he struggled with a severe cocaine and alcohol addiction.

"Cocaine for me was a place to hide," he told People in 1988. "Most people get hyper on coke. It slowed me down." He kicked his habit when his first wife became pregnant with their eldest son, Zachary, in 1982.

Robin was sober for 20 years before he relapsed in 2003 on location in Alaska. "One day I walked into a store and saw a little bottle of Jack Daniel's," he recalled in a 2013 Parade article. "And then that voice — I call it the 'lower power' — goes, 'Hey. Just a taste. Just one.' ... It escalated so quickly. Within a week, I was buying so many bottles I sounded like a wind chime walking down the street."

He didn't take up cocaine again, because "I knew that would kill me," he told The Guardian of his relapse. Robin entered rehab in 2006. "It was not an intervention so much as an ultimatum," he admitted. 

In 2014, two months before his death, Robin checked himself into a treatment center to "focus on his commitment" to overcome his addictions. "Robin is simply taking the opportunity to fine-tune and focus on his continued commitment, of which he remains extremely proud," his rep said at the time.

Robin died by suicide on August 11, 2014, at the age of 63. Before his death, he had been struggling with tremors, anxiety, paranoia, and depression, and was misdiagnosed with Parkinson's disease. An autopsy revealed he was suffering from undiagnosed Diffuse Lewy Body Dementia.

David Cassidy played Keith Partridge in The Partridge Family before he became a pop icon, but he stopped touring and retreated from the spotlight in 1974 after a 14-year-old fan, Bernadette Whelan, died after being crushed in a crowd surge during his concert at London's White City Stadium on May 26, 1974.

Despite his success, he faced significant financial distress during his later years and filed for Chapter 11 bankruptcy in 2015, with debts of $2.1 million. 

He has also had several brushes with the law. Between November 2010 and January 2014, he was charged with a DUI three times and was ordered to rehab as part of his sentence. David openly admitted that he had a drinking problem and revealed to Piers Morgan in 2014 after his third arrest: "If I take another drink, I'm going to die, physically, mentally, emotionally, spiritually. I'm dead."

In February 2017, David claimed that he had dementia after he forgot his words and appeared physically unstable during performances in California. However, after he died on November 21, 2017, at age 67 after suffering liver and kidney failure, a posthumous documentary, David Cassidy: The Last Session, filmed just before his death, revealed he had lied about the diagnosis to cover up his drinking. 

"I did it to myself, to cover up the sadness and the emptiness. There is no sign of me having dementia at this stage of my life," he said. "It was complete alcohol poisoning. And the fact is, I lied about my drinking."

Erin Moran rose to stardom when she was just 13 after landing the role of Joanie Cunningham on Happy Days in 1974. However, behind-the-scenes, Erin was feeling Hollywood pressure: in a 1983 interview, Erin claimed that by the time she had turned 15, producers "suddenly wanted me to lose weight and become this sexy thing."

In 1982, Erin began starring in the spin-off Joanie Loves Chachi and later claimed that she would have preferred to stay as a cast member of Happy Days. "I liked working with the people. But I didn't even want to do it," she said. "I wanted to stay on Happy Days."

The show was canceled after 17 episodes, and Erin's career never recovered; she struggled financially, and in 2011, she joined several co-stars in a $10 million lawsuit against CBS for unpaid royalties. In 2012, they were each awarded $65,000 after settling out of court.

That same year, it emerged that Erin had been served eviction papers and her California home had been foreclosed on in 2010. She and her husband, Steve Fleischmann, were effectively homeless before they moved into a trailer park in Indiana with his ailing mother.

In late 2016, Erin was diagnosed with stage 4 squamous cell carcinoma (throat cancer), a diagnosis she didn't reveal publicly. She died on April 22, 2017, at age 56, with police in Harrison County, Indiana, confirming "no illegal narcotics were involved in her death."

The clarification came after speculation around her cause of death was amplified by comments made by her former co-star Scott Baio, who said: "For me, you do drugs or drink, you're going to die. I'm sorry if that's cold, but God gave you a brain, gave you the will to live and thrive, and you gotta take care of yourself." An autopsy confirmed she died of natural complications from advanced cancer.

Fred Berry became a star playing the red-beret-wearing Freddie 'Rerun' Stubbs on the '70s sitcom What's Happening! and was a millionaire by age 29, but he later confessed he was "empty inside" and battled with addiction.

"I was a millionaire by the time I was 29," he told People in 1996. "The stress of success got to me. The fat jokes got to me. And I got heavily into drugs and alcohol. I was empty inside."

Fred had been "addicted to drugs and alcohol for 10 years" and once claimed to the Cincinnati Call and Post that he "probably spent a million dollars partying," before admitting he "tried to commit suicide three times."

Fred was also married six times, to four women, remarrying his first two wives twice each. By 2002, he had separated from his sixth wife, whom he didn't name because "she's been trying to get her 15 minutes of fame from me off of my name and my career ever since we got married. I don't want to give her that pleasure."

The actor eventually became sober and worked as a Baptist minister. "I'm not the ordinary orthodox pat-you-on-the-head type," he told CNN. "I'm the type of minister that will get in your face. I'm real because it's a real world out there."

Fred died aged 52 on October 21, 2003, of natural causes. He was found in his Los Angeles home and had been suffering from health issues, and had a stroke shortly before his death.

Susan Dey was just 17 when she landed the role of Laurie Partridge in the hit '70s TV show The Partridge Family. The brunette beauty's journey from teen idol to acclaimed actress was nothing short of rocky, after she developed an eating disorder during the show's run, which plagued her for years to come. 

"I'm not in the clear yet – I'm still trying to overcome my anorexia," she told The Enquirer in 1993, as per 9Honey. "It's something that has been plaguing my life. Beating a severe eating disorder is something you cannot do alone."

She experienced the darker side of fame when the tabloid media revealed that she was a frequent attendee of Alcoholics Anonymous meetings, which she said was a major breach of her privacy. 

"I usually don't talk about it because I feel it's my business and nobody else's," she shared with Parade. "After I had been sober for a year, I was given a cake at [an AA] meeting. The tabloids ran a big story about it. I was furious that they had planted an informant in my AA group."

Susan ended her run on The Partridge Family in 1974 and went on to spread her wings in Hollywood with roles in Little Women, The Brady Bunch, and LA Law, but chose to leave Hollywood altogether in 2004, with an appearance in two episodes of Third Watch marking her final acting credit.