The 18-year-old singer - who has been dating the 31-year-old 'That 70S Show' actor since January - reportedly called time on the couple's relationship because their 13-year age gap meant they were "in completely different places in their lives".
A source told the New York Post newspaper: "The age difference meant they were in completely different places in their lives."
However, this isn't the only issue Demi - who was admitted to rehab last November to receive treatment for "emotional and physical issues" - has had to deal with of late.
Her mother Dianna Hart de la Garza has reportedly decided to get treatment for her own issues at an undisclosed location.
The insider added: "It has been a tough year for Demi, and her mom has been a constant source of support. But fame has also taken its toll on her family. Now that Demi is strong again, her mom could take some time to deal with her own issues."
Demi recently announced she discovered she suffered from bipolar disorder while receiving treatment in the residential Clinic.
She said: "I never found out until I went into treatment that I was bipolar. Looking back it makes sense. There were times when I was so manic, I was writing seven songs in one night and I'd be up until 05.30 in the morning. I feel like I am in control now where my whole life wasn't in control."