Addiction is the continued use of a mood altering substance or behaviour despite adverse consequences, or a neurological impairment leading to such behaviors.

Addictions can include, but are not limited to, alcohol abuse, drug abuse, exercise abuse, and gambling. Classic hallmarks of addiction include: impaired control over substances/behavior, preoccupation with substance/behavior, continued use despite consequences, and denial. Habits and patterns associated with addiction are typically characterized by immediate gratification (short-term reward), coupled with delayed deleterious effects (long-term costs).Physiological dependence occurs when the body has to adjust to the substance by incorporating the substance into its 'normal' functioning. This state creates the conditions of tolerance and withdrawal. Tolerance is the process by which the body continually adapts to the substance and requires increasingly larger amounts to achieve the original effects. Withdrawal refers to physical and psychological symptoms people experience when reducing or discontinuing a substance the body had become dependent on. Symptoms of withdrawal generally include but are not limited to anxiety, irritability, intense cravings for the substance, nausea, hallucinations, headaches, cold sweats, and tremors.

Russell Edward Brand (born 4 June 1975) is an English comedian, actor, columnist, singer, author and radio/television presenter.

Brand achieved mainstream fame in the UK in 2004 for his role as host of Big Brother spin-off, Big Brother's Big Mouth. His first major film role was in the 2007 film St Trinian's. He became known to American audiences when he got a major role in Forgetting Sarah Marshall which led to a starring role in 2010's Get Him to the Greek. He has also been a voice actor for animated films such as 2010's Despicable Me and the 2011 film Hop. He starred in the 2011 remake of the 1981 Dudley Moore film Arthur.

Brand is noted for his eccentricity and his controversies in the British media, including his dismissal from MTV for dressing up as Osama bin Laden and controversies while presenting at various award ceremonies, as well as his former substance abuse. The 2008 prank telephone calls he made to Andrew Sachs while co-hosting The Russell Brand Show with Jonathan Ross led to his resignation from the BBC and major policy changes in that organisation. His prior drug use, alcoholism and promiscuity influenced his comedic material and public image. He married American pop singer Katy Perry in October 2010, and filed for divorce from her in December 2011; the divorce was finalised in 2012.

Anthony Ryan Leslie, known professionally as Ryan Leslie, (born September 25, 1978) is an American record producer, multi-instrumentalist, rapper, entrepreneur, and singer. Founder of the media company NextSelection Lifestyle Group, Leslie has produced singles for a number of artists in a variety of genres ranging from R&B/Hip-Hop to Pop to Gospel. From 2005–2006, he had his most commercial success to date with NextSelection/Bad Boy/Atlantic recording artist Cassie and her single "Me & U". Leslie's debut album, Ryan Leslie (2009), features the songs "Diamond Girl," "Addiction," and "How It Was Supposed To Be." He was nominated for a Grammy in 2011.

Ryan Leslie was born into a multicultural family. Leslie is the oldest son of mother (Evangeline) Mooi Leslie who is of Caribbean Dutch, Chinese, and African descent, and father Clement Leslie who is from Barbados and of Irish ancestry, raised in Trinidad.^{[citation needed]} His parents are Salvation Army officers who frequently relocate for work. Ryan has lived in various states, cities, and countries. At an early age, Leslie taught himself how to play the piano under the guidance of Marc Styles. He developed the ability to recite music, as well as arrange chords to create songs. At the age of 14, Leslie scored a 1600 on his SATs—a perfect score—while attending Bear Creek High School, in Stockton, CA. In 1993, he applied to four University of California campuses as well as Stanford, Yale and Harvard. In his application essays he explained his interest in matriculating from his junior year in high school without having earned a diploma. He was accepted to all except for Stanford. He ultimately decided to attend Harvard College. At the age of 19, Leslie graduated from Harvard with a degree in Government, concentrating in Political Science and Macroeconomics. During his commencement ceremonies, Ryan delivered the prestigious Harvard Oration.