Britney Spears’ attorney Leon Gladstone has revealed that his client “changed” dramatically following her split from Justin Timberlake.

The songstress’ former manager Sam Lufti has sued the pop princess and her parents for defamation and breach of contract.

In court on Friday Leon addressed Britney’s public meltdown, which took place five years ago.

Sam’s lawyer Joseph Schleimer attributed her breakdown to amphetamine abuse on Thursday.

TMZ reports that Leon claimed Britney’s mental health issues stemmed from heartbreak, as her break-up with Justin in 2003 took a toll on her.

"[Britney] changed [and] became depressed,” Leon revealed to jurors in his opening statement.

“[They] had a big relationship, and it ended painfully. In 2003 her parents noticed that she had changed over the breakup of her and Justin and noticed she was depressed…. [Britney] went to Vegas and got married to a childhood friend for 55 hours and they realised that she was becoming distant with her parents and become concerned she was using illegal substances."

In 2007 Britney shaved her hair off as part of her public meltdown.

Sam’s counsel asserted that the star decided to go bald to prevent drug testing.

Apparently she was convinced authorities would find remnants of the drug in her hair follicles and she would lose custody of her children as a result.

The trial continues.