Gaming disorder, also known as video game addiction, has been officially added to the International Classification of Diseases (ICD), which serves as a guide for doctors in diagnosing diseases.

Last Saturday, the World Health Organisation (WHO) approved the latest catalogue of diseases and injuries.

The updated list, named ICD-11, was approved by WHO's 194 member states, including Singapore, after more than a year of deliberation. It will come into effect in January 2022.

Here are six things to know about the ICD.

1. What is the ICD and what does it do?

The ICD defines and classifies diseases, disorders, injuries and other related health conditions in a way that allows the universal mapping of health trends, and the comparison of data.

Countries use the system to report mortality data, which is the primary indicator of health status.

The first international classification edition, known as the International List of Causes of Death, was adopted by the International Statistical Institute in 1893.

In 1948, WHO was entrusted with the ICD and it published the sixth version, the ICD-6, that year.

The 11th revision to the ICD was released on June 18 last year for member states to prepare for its implementation and translate it into their national language.

The previous edition, ICD-10, was released in 1990.

Members states unanimously agreed to the ICD-11 last Saturday at the World Health Assembly in Geneva.

2. How is the ICD organised?

The ICD provides a common vocabulary for doctors, researchers, policymakers and organisation around the world through codes.

It is also used by health insurers whose reimbursements depend on ICD coding.

For instance, gaming disorder has the code 6C51.

There are 55,000 codes in the ICD-11, compared with 14,400 in the previous editions.

3. Is work stress a medical condition?

No, burnout is considered an "occupational phenomenon" that could lead someone to seek care but it is not considered a medical condition.

WHO has defined burnout as "a syndrome conceptualised as resulting from chronic workplace stress that has not been successfully managed".

The organisation had mistakenly said it had listed burnout in its ICD for the first time on Monday.

Patients suffering from burnout display these three symptoms:

1. Feelings of energy depletion or exhaustion

2. Increased mental distance from one's job, or feelings of negativism or cynicism related to one's job

3. Reduced professional efficacy

4. What conditions are newly classified?

For the first time, WHO has classified gaming disorder as an addictive behaviour disorder in the ICD.

Those diagnosed with gaming disorder show a pattern of persistent or recurrent gaming behaviour, which may be online or offline.

However, gaming disorder is more than just playing video games a lot.

It is characterised by gaming behaviour that impairs other aspects of life over a period of time. ICD has listed these as symptoms:

1. Impaired control over gaming

2. Increasing priority given to gaming to the extent that gaming takes precedence over other life interests and daily activities; and

3. Continuation or escalation of gaming despite the occurrence of negative consequences.

The ICD-11 also has a new chapter on traditional medicine.

5. Were there conditions that were reclassified?

Yes, gender incongruence and sexual dysfunction are two examples.

These now sit under sexual health conditions, and are no longer described as a mental disorders under the ICD-11.

Some experts have said that classifying these as mental disorders have led to the stigmatisation of these patients and discriminatory policies.

Excessive sexual drive has also been reclassified as compulsive sexual behaviour disorder.

It falls under an "impulse control disorder" rather than a disorder related to addiction.

Impulse disorders are defined by the repeated failure to resist a craving despite knowing the action can cause long-term harm.

6. Other conditions you may not have known were in the ICD-11 and their codes

PJ00: Victim of lightning

PD7Z: Being hit by spacecraft

NE40: Frostbite

ND73.20: Hairball in the stomach

6B24: Hoarding disorder

QC30: Malingering, or pretending to be ill

QE41: Problems associated with being in prison