Scientists have been studying addiction for years in order to improve treatments for harmful behaviour. They have found that powerful memories, often of highly pleasurable or intense experiences, underlie addiction. During such experiences the brain releases a chemical called dopamine that creates a reward circuit in the brain, by logging the intense experience as pleasurable and an important action to be repeated.

Dopamine release generally occurs in a region called the ventral tegmental area (VTA). In response to this, epigenetic changes happen in brain nerve cells to form reward memories. These chemical changes are a mix of DNA methylation and demethylation, which either turns genes off or on.

Such a system allows changes in how genes are expressed in cells without altering our genetic code, and forms a type of genetic memory.

Addiction to all four major classes of abused substances - psychostimulants, opiates, alcohol and nicotine - has been linked to the same parts of the brain associated with normal reward processing.

Because of this, scientists originally thought that drug addiction took over normal reward memory nerve pathways. However, a more nuanced picture is now emerging.

In normal reward processing, the VTA signals to another region of the brain called the nucleus accumbens (NAC).

So when scientists blocked methylation changes in both these regions in rat brains, they expected to block reward memory formation.

Surprisingly, this happened only when the VTA was blocked, but not the NAC. This points to a distinction in the chemical regulation of reward circuits in normal reward responses versus addiction responses.

Dr Jeremy Day from the University of Alabama at Birmingham, who led the study, says: "Although drug experiences may co-opt normal reward mechanisms to some extent, our results suggest they also may engage entirely separate epigenetic mechanisms that contribute only to addiction and that may explain its strength."

According to the Central Registry of Drug Abuse, opiates - such as heroin - have been the most common drug abused in Hong Kong; however, rates of heroin abuse have been dropping.

In its place, psychotropic substances - which cross the blood-brain barrier and act primarily upon the central nervous system - such as cocaine, ketamine and methamphetamine, have become the drugs of choice.

Alcohol consumption peaked in 2008 before decreasing in recent years, according to a survey by the Health Department. Smoking has seen a falling trend: cigarette smoking prevalence dropped to a 30-year low of 11.1 per cent in 2010.

While abusing drugs, alcohol and nicotine typically kills you gradually, another well-known addiction that can kill quickly is gambling, whether in casinos or on the stock market.

In Hong Kong, a 2010 study found that almost half of gambling suicides in the city were associated with large gambling debts.

Now, a new form of addiction is ensnaring youths and adolescents with the spread of the internet, gaming technology and smartphones.

Professor Daniel Shek Tan-lei at Polytechnic University conducted a study in 2011 that found 26.7 per cent - just over a quarter - of 3,500 students interviewed were considered addicted to the internet.

Dr Alain Dagher, of McGill University, believes that abnormal interactions between different decision-making regions in the brain are the underlying cause of addiction.

A specific region in the brain called the dorsolateral prefrontal cortex regulates feelings of craving in response to cues. For example, a smoker craves a cigarette when they see or smell someone else smoking. By visualising how an addicted person perceives a substance, the imaging results can be used to predict consumption.

Applying a technique called transcranial magnetic stimulation, a method that uses magnets to induce weak electric currents in the brain without any form of surgery, the dorsolateral prefrontal cortex can be inactivated - and the craving response can be altered.

Dagher says: "Policy debates have often centred on whether addictive behaviour is a choice or a brain disease. This research allows us to view addiction as a pathology of choice. Dysfunction in brain regions that assign value to possible options may lead to choosing harmful behaviour."

Treatment of addiction requires a multi-pronged approach. These include the gradual reduction of the abused substance with the aim of total abstinence, and counselling services. Experts agree a key aspect of addiction treatment is social and family support.

Dr Bonnie Lee, associate professor at the University of Lethbridge in Canada, believes that instead of treating addiction in individuals, help should be administered at the group level.

Lee has developed Congruence Couple Therapy, a model adopted by treatment agencies in Canada, and which Lee has taken to places around the world, including Hong Kong.

"One could say relationship breakdown is the root of addiction in most cases, often originating in childhood with abuse, neglect and abandonment," she says.

"I like to see how family members talk to each other. Like a stage director, I reshape the family interactions to promote mutual understanding of fears and hurts, as well as the sharing of hopes and wishes.

"This collaborative spirit then propels the therapy forward because there is hope when everyone works together with realistic expectations."

Lee believes congruence therapy is particularly apt for Asia. "Asian values prize the family as the cornerstone for individual and societal harmony and well-being.

"The Taoist worldview of interconnections resonates with contemporary 'systems thinking' in addressing the individual as inseparable from couple and intergenerational relationships.

"There is a lot in congruence therapy that would appeal to Asian clinicians and clients."

To treat addiction in youths, Shek also believes family support to be paramount. Referring to youth development programmes in Hong Kong, he says: "Most focus on life skills training, such as emotional management. Family intervention is also an effective intervention direction."

In Hong Kong, according to Shek's 2011 report, a youth development programme aimed at secondary school students called Project PATHS made good headway in reducing adolescents' delinquent behaviour and substance use, while increasing psychosocial competencies and their ability to control internet use.

As time passes, new types of addiction may become traditional, while newer ones appear on the horizon.

Although addiction may be multifaceted, scientists are discovering common underlying pathways in the brain that can help shape treatment options.

By focusing rehabilitation efforts on family and social support, we are becoming better equipped to battle addiction, regardless of its shape or form.