It’s thought one in five teenagers will dabble with drugs at some point.

A 2021 survey of secondary school pupils in England (aged 11 to 15) found 18% reported they had ever taken drugs – 12% had taken drugs in the past year, and 6% in the last month.

Ryan Erispe, from The Cabin Drug and Alcohol Rehab in Thailand, said the most abused substances by teens include alcohol, marijuana, and nicotine, as well as prescription drugs like painkillers or stimulants, and even over-the-counter medications like cough syrup.

There are also online social media ‘challenges’ encouraging dangerous behaviours involving household cleaning products. One such trend, dubbed ‘dusting’, saw a 19-year-old die after inhaling a keyboard cleaning product delivered to the family home.

How can you tell if your teen is doing drugs?

‘Normal’ teen behaviour is “temporary, explainable, and improves with guidance or time,” said Erispe. On the other hand, drug-related behaviour tends to be “persistent, extreme, secretive, and worsens despite parental involvement”.

The signs of substance abuse in teens can be physical, behavioural, emotional, or social, and vary depending on the type of drug being used.

Here are some of the signs that Erispe has become familiar with in his line of work:

1. Bloodshot eyes

Bloodshot eyes are a physical sign of drug use, “characterised by the redness or glassiness of the eyes caused by the enlargement or irritation of blood vessels in the white part of the eye”, he said.

It occurs after using substances like marijuana, alcohol, or stimulants, which affect blood pressure, cause dryness, or dilate blood vessels.

2. Mood swings

Mood swings are marked by rapid and unpredictable changes in a person’s emotional state, such as sudden shifting from happiness to anger, or from calmness to irritability.

“The changes are triggered by the way drugs affect brain chemistry, which interferes with neurotransmitters like dopamine or serotonin,” said Erispe.

While mood swings alone might not be a sign of drug use (because........

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