In 2007 and 2008, Lovato played the role of Charlotte Adams on the Disney Channel short series As the Bell Rings. On the same day in summer 2007, she auditioned for the channel's television film Camp Rock and the television series Sonny with a Chance, and got both parts. Lovato received the lead role in Camp Rock, playing aspiring singer Mitchie Torres. The movie premiered on June 20, 2008 to 8.9 million viewers, and was complimented by David Hinkley of Daily News for following a storyline similar to that of High School Musical. Its soundtrack was released on June 17, 2008, though its music was deemed less current than that of High School Musical. Gillian Flynn from Entertainment Weekly opined that Lovato's acting skills were underwhelming, commenting that she "has the knee-jerk smile of someone who is often told she has a great smile". She provided vocals for four of the songs featured on its soundtrack, including "We Rock" and "This Is Me". That summer, Lovato embarked on her Demi Live! Warm Up Tour prior to the release of her debut album; she also appeared during the Jonas Brothers' Burnin' Up Tour.
In 2009, Lovato, with Selena Gomez, Miley Cyrus, and the Jonas Brothers, recorded "Send It On", a charity single that served as the theme song for environmental organization Disney's Friends for Change. All of the song's proceeds were sent to environmental charities supported by the Disney Worldwide Conservation Fund. Bill Lamb of About.com was pleased to see the network's talents collaborate for the cause, but felt that the track itself was "tedious". On February 8, Lovato's Disney Channel sitcom Sonny with a Chance premiered, in which her character Sonny Munroe became the newest cast member on the show-within-a-show So Random!. Lovato's acting abilities were described by Robert Lloyd of The Los Angeles Times as being "very good" and drew favorable comparisons to Hannah Montana actress Miley Cyrus, while Carey Bryson of About.com placed particular praise on the respectful and self-confident role model set by her character Munroe. That June, she co-starred in the Disney Channel film Princess Protection Program as Princess Rosalinda, alongside Selena Gomez. It is the third highest-rated Disney Channel Original Movie, premiering with 8.5 million viewers. The film was appreciated by Bryson for incorporating a "cheesy, unrealistic, and sometimes downright silly" plotline typical of Disney films with a positive message of valuing friendship.
Camp Rock 2: The Final Jam premiered on September 3, 2010, where Lovato reprised her role as Mitchie Torres. Critics were ambivalent towards its storyline; the film holds a 40% critical rating on Rotten Tomatoes. However, Lovato's performance was noted by Jennifer Armstrong from Entertainment Weekly as "dependably appealing". It premiered to 8 million viewers, becoming the number one cable television movie of the year by number of viewers.
Also that April, Lovato announced her departure from Sonny with a Chance, effectively putting her acting career in hiatus and ending the series; she commented that "...it's kind of sad for me that a chapter of my life has ended but there couldn't be a better time for me to move on...I don't think going back to Sonny would be healthy for my recovery...Being in front of a camera would make me nervous." She later stated she was willing to return to acting when she felt confident about doing so. Her exit led to the creation of the spin-off So Random!, which focused on the sketches of the former show-within-a-show. The show featured the former Sonny cast members (with exception of Lovato), however was later cancelled after one season.
Lovato's debut album Don't Forget was released on September 23, 2008. Max Paradise from Sputnikmusic appreciated the enjoyable nature of the record, while Michael Slezak of Entertainment Weekly was more critical of its lyrical content and Lovato's vocals. It debuted at number two on the Billboard 200, with 89,000 copies in first-week sales. Ten of its songs were co-written with the Jonas Brothers. The album has since been certified Gold by the Recording Industry Association of America (RIAA), having sold over 500,000 units in the country. Its lead single "Get Back" was praised for displaying prominent pop rock styles, and reached a peak position of number 43 on the US Billboard Hot 100. Similarly, the second and final single "La La Land" was appreciated for its strong showing of rock elements. The track peaked at number 52 in the United States.
Lovato's second studio album Here We Go Again was released on July 21, 2009. She described its acoustic-sounding styles as being similar to the works of John Mayer. The album received favorable reviews from critics; they appreciated the enjoyable nature and pop rock elements of the record, echoing sentiments expressed for Don't Forget. It debuted atop the Billboard 200 with 108,000 copies in first-week sales, becoming her first number one album in the country. Prior to the album's release, Lovato embarked on the Summer Tour 2009 for promotion. Its singles "Here We Go Again" and "Remember December" were recognized by Stephen Thomas Erlewine as highlights from the project. Having peaked at number 15 on the Billboard Hot 100, the former became Lovato's first top 40 hit as a solo artist; the latter peaked at number 80 on the UK Singles Chart.
In March 2010, Lovato and Joe Jonas recorded "Make a Wave" as a second charity single for Disney's Friends for Change. Later that year, she headlined her first international tour, the South American Tour; she later joined the Jonas Brothers Live in Concert tour as a special guest. In May, Lovato appeared as a guest star on the episode "Shiny Happy People" during the sixth season of the medical drama series Grey's Anatomy; she portrayed a teenage schizophrenic patient named Hayley. Critics complimented the versatility attempted in portraying a foreboding character, but were underwhelmed by her acting and felt that her appearance was designed to attract viewers.
Camp Rock 2's accompanying soundtrack was released on August 10; Lovato provided vocals for nine songs, including "Can't Back Down" and "Wouldn't Change a Thing". The soundtrack debuted at number three on the Billboard 200, with 41,000 copies in first-week sales. The Jonas Brothers' 2012 World Tour was reworked to incorporate Lovato and the rest of the film's cast; it began on August 7, two weeks later than planned. The Sonny with a Chance soundtrack was released on October 5; Lovato provided vocals for four tracks, including "Me, Myself and Time". It debuted at number 163 on the Billboard 200, making it Lovato's lowest debut and peaking soundtrack there.
Lovato's third studio album Unbroken was released on September 20, 2011. Having begun work on the record in July 2010, she featured less pop rock styles and experimented with R&B elements. The transition received mixed reviews from critics, who identified a growth in musicianship in light of her personal struggles, but opined that the music was more generic than her previous efforts. Its lead single "Skyscraper" received universal acclaim for its message of self-worth and confidence, and peaked at number 10 on the Billboard Hot 100. Its second and final single "Give Your Heart a Break" drew favorable comparisons to the works of Cyndi Lauper and Madonna from the 1980s, and peaked at number 16 in the United States. Both singles were certified platinum in the United States. Lovato held her Summer Tour 2012 from June through September. In July 2012, "Skyscraper" was nominated for "Best Video With a Message" at the 2012 MTV Video Music Awards, which she won.
On December 24, 2012, Lovato released a video of her performing "Angels Among Us" on her YouTube account, which she dedicated to the victims of the Sandy Hook Elementary School shooting. On February 24, "Heart Attack" was premiered on On Air with Ryan Seacrest as the lead single from her fourth album Demi. It was applauded for incorporating both electropop styles and acoustic instrumentation by way of guitars and drums. The song debuted at number 12 on the US Billboard Hot 100 with first-week sales of 215,000 copies. In doing so, it became the third-highest opening-week sales figure of 2013, behind Justin Timberlake's "Suit & Tie" and Ariana Grande's "The Way". Since, the track peaked at number 10 in the United States, becoming Lovato's third top ten success in her primary market. Additionally, it attained international success in several markets, including Australia and Spain. She performed at the Twin Towers Alive Concert 2013 at the Petronas Twin Towers in Kuala Lumpur, Malaysia on March 22, 2013 alongside Backstreet Boys.
Demi was released on May 10, 2013. Straying from the R&B styles featured in Unbroken, the record predominantly incorporates electropop and teen pop elements. The transition was appreciated by Jon Carmichael from The New York Times for its fun nature, though Entertainment Weekly opined that it developed a less-mature image for Lovato. It debuted at number 3 on the Billboard 200 with first-week sales of 110,000 copies, becoming her best-selling debut week of her career. The record attained acceptable international success, appearing in the top ten in territories including New Zealand and Spain. On June 11, Lovato released an iBooks-exclusive e-book, also titled Demi.
In January 2013, it was reported that Lovato had been residing in a sober living facility in Los Angeles for more than a year, feeling it was the best way to avoid returning to her addictions and eating disorder.
On October 30, 2010, Lovato withdrew from the Jonas Brothers Live in Concert to enter a treatment facility to confront "physical and emotional issues". Reports indicated that Lovato decided to enter treatment after punching female back-up dancer Alex Welch during a confrontation, which led to an intervention by her family and management; she later took "100 percent, full responsibility" for the incident. A financial settlement was reached in December, a portion of which was donated to charity. On January 28, 2011, Lovato completed her inpatient treatment at the Timberline Knolls facility and returned home to Los Angeles, where she would "continue to see doctors" to "help her work on the issues she confronted in treatment". Lovato later acknowledged having suffered from bulimia, self-injury, and "self-medicating" with drugs and alcohol, which she stated was "like a lot of teens do to numb their pain". Lovato added that she had "basically had a nervous breakdown" and was diagnosed with bipolar disorder during treatment, also noting that she had gained weight during the process. In April, she became a contributing editor for Seventeen magazine, where she discussed her personal struggles, directed towards teenage girls.
Demi dated Joe Jonas from January 2010 till May 2010. Demi is currently dating BTR's Logan Henderson from November 2011 till present.