Two years ago, just one person was caught abusing new psychoactive substances or NPS.
Last year, this figure rose to 343, as such drugs flooded the market in different formulations worldwide.
NPS are relatively new drugs meant to mimic older, controlled drugs, such as methamphetamine, heroin, cannabis and cocaine.
Singapore has listed an increasing number of NPS as controlled drugs, though the NPS market continues to evolve.
Other names of NPS include legal highs, K2, bath salts and synthetic cannabis.
Dr Mohamed Zakir Karuvetil, associate consultant with the National Addictions Management Service at the Institute of Mental Health, said: "These substances are often sold as legal products without any safety information or indication of the presence of psychoactive substances in them. This makes them dangerous to consume."
Right now, it is difficult to know the common effects of these drugs as they keep changing.
Dr Karuvetil said laboratory analyses of NPS have revealed that their contents can differ markedly even within the same brand name.
But based on what is known about NPS, they are chemically similar to other strong and addictive psychoactive drugs, he noted.
The physical withdrawal symptoms vary from mild to severe, depending on the NPS used and individual vulnerability.
As the chemicals vary significantly, there are no typical withdrawal symptoms. In most cases, regular use might lead to headache, agitation, tremor and insomnia when stopped, Dr Karuvetil said.
In other cases, there may be acute mental-state changes, with paranoia, thought disorder, hallucinations, low mood, suicidal thoughts and anxiety.
Compared with other controlled drugs, NPS may appear to have milder symptoms of physical withdrawal.
But their symptoms of psychological withdrawal, such as agitation, anger, anxiety, depressed mood and cravings, are similar to withdrawal from other drugs such as cannabis, and may need symptomatic treatment and support.
"Some vulnerable individuals can be more sensitive to the addictive nature of NPS and may, therefore, develop medical complications, such as extreme paranoia, hallucinations, suicidal tendencies and altered mental status," said Dr Karuvetil.
Addiction to NPS will also have more serious, long-term mental-health problems, such as depressive disorder, anxiety disorder, psychosis and memory problems, which will affect almost all areas of a person's life, he warned.
"Consuming these largely unknown substances for leisure purposes is therefore risky and also associated with short-and long-term negative consequences."
Other countries have reported fatal cases of young people abusing NPS.
Such abuse may also get one into trouble with the law as NPS may contain illicit substances.
According to the Alcohol and Drug Foundation in Australia, the packaging of these drugs is often misleading and does not list all the ingredients or the correct amounts, which can make it easy for abusers to overdose on them.
It also said that negative side effects and overdose are more likely when NPS are taken in combination with alcohol or other drugs.
If one overdoses on NPS, one could have serious health risks as there is a lack of standardised laboratory tests to detect the presence of NPS in body fluids, said Dr Karuvetil.
Thus, medical emergency services may be unable to administer appropriate and essential life-saving treatment in suspected overdose cases, he said.