Lindsay Lohan has "nothing to go out for anymore".

The 22-year-old actress - who has been to rehab three times to seek help for her drug addictions - credits girlfriend Samantha Ronson for helping her straighten out her life.

Speaking about her punishments for cocaine use and driving under the influence (DUI) - she spent a day in jail and did 10 days community service in 2007 - and her time in rehab, Lindsay added to US TV show 'Extra': "I've learned my lesson at an early age and I am very thankful for that."

Lindsay also revealed she wants to do a duet with her younger sister Ali on her upcoming third studio album 'Spirit in the Dark', for which a release date has yet to be set.

She said: "Ali has a beautiful voice. I'm a big fan of my sister - she's beautiful and I love her."