For many people the concept of addiction involves taking drugs such as alcohol, nicotine, cocaine and heroin.
But in this week's Scrubbing Up, gambling studies expert Mark Griffiths warns that if the rewards are there people can become addicted to almost anything.
For the past 25 years I have been studying gambling and I passionately believe that gambling at its most extreme is just as addictive as any drug.
The social and health costs of problem gambling are large and have many things in common with more traditional addictions, including moodiness, relationship problems, absenteeism from work, domestic violence, and bankruptcy.
Health effects - for gamblers and their partners - include anxiety and depression, insomnia, intestinal disorders, migraine, stress related disorders, stomach problems, and suicidal thoughts.
If behaviours like gambling can become a genuine addiction, there is no theoretical reason why some people might not become genuinely addicted to activities like video games, work or exercise.
Research on pathological gamblers has reported at least one physical side effect when they undergo withdrawal, including insomnia, headaches, loss of appetite, physical weakness, heart palpitations, muscle aches, breathing difficulty, and chills.
In fact, pathological gamblers appear to experience more physical withdrawal effects when attempting to stop their behaviour when compared directly with drug addicts.
'Most important thing'
But when does an excessive healthy enthusiasm become an addiction?
Excessive behaviour on its own does not mean someone is addicted.
I can think of lots of people who engage in excessive activities but I wouldn't class them as addicts as they don't appear to experience any detrimental effects from engaging in the behaviour.
In a nutshell, the fundamental difference between excessive enthusiasm and addiction is that healthy enthusiasms add to life whereas addiction takes away from it.
For any behaviour to be defined as addictive, there have to be specific consequences such as it becoming the most important activity in the person's life or being the way they improve their mood.
They may also begin to need to do more and more of the activity over time to feel the effects, and experience physical and psychological withdrawal symptoms if they can't do it.
This may lead to conflict with work and personal responsibilities, and people may even experience "relapses" if they try to give up.
The way addictions develop - whether chemical or behavioural - is complex.
Addictive behaviour develops from a combination of a person's biological/genetic predisposition, the social environment they were brought up in, their psychological constitution - such as personality factors, attitudes, expectations and beliefs, and the activity itself.
Many behavioural addictions are "hidden" addictions. Unlike, say, alcoholism, there is no slurred speech and no stumbling into work.
However, behavioural addiction is a health issue that needs to be taken seriously by all those in the health and medical profession.
If the main aim of practitioners is to ensure the health of their patients, then an awareness of behavioural addiction and the issues surrounding it should be an important part of basic knowledge and training.
Behavioural addictions can be just as serious as drug addictions.