Psychoactive substances can change perception, mood, alertness, behaviour or consciousness. That description covers a very broad range of drugs, and grouping them together can sometimes hide more than it reveals.
A stimulant such as cocaine does not create the same risks as a dissociative drug such as ketamine. LSD has a very different acute profile from methamphetamine. MDMA sits somewhere else again, combining stimulant effects with substantial changes in serotonin signalling.
This section of PlusGBUK is organised around those differences. Each substance guide looks at what the drug does, the risks that matter most, patterns of dependence where relevant, interactions, emergency warning signs and the current UK legal position.
Substance guides
Ketamine
Ketamine is a dissociative anaesthetic with legitimate medical uses as well as non-medical use. Repeated exposure can cause serious urinary tract and bladder damage, and dependence can develop in people using frequently.
Our ketamine hub covers effects, bladder damage, dependence, withdrawal and UK law.
Cocaine
Cocaine is a short-acting stimulant, but its cardiovascular effects can be significant. Repeated dosing can increase strain on the heart and contribute to anxiety, sleep disruption, dependence and compulsive use.
Our cocaine section includes cocaine effects, health risks, cocaine and alcohol, dependence and UK law.
MDMA and Ecstasy
MDMA is a stimulant and empathogenic drug associated with increased energy, emotional openness and altered sensory experience. Acute risk is strongly influenced by temperature, exertion, repeated dosing and fluid balance.
Our MDMA section covers effects, dependence, product identification limits and UK law.
LSD
LSD is a potent psychedelic. Its main risks are not the same as those associated with stimulants or sedatives. Prolonged perceptual changes, panic, disorientation, unsafe behaviour and persistent psychological symptoms are more relevant concerns.
Read our guides to LSD effects, duration, blotter identification and UK law.
Crystal Methamphetamine
Methamphetamine is a long-acting stimulant that can produce prolonged wakefulness, cardiovascular stress, agitation and severe sleep disruption. Dependence can become entrenched, particularly with repeated or high-intensity use.
Our methamphetamine section includes effects, dependence, appearance and identification and UK law.
Why we separate effects from product identity
One of the most common mistakes in drug information is treating a visual description as though it identifies a substance.
It does not.
Colour, crystal shape, tablet logo, powder texture or packaging cannot establish chemical identity, purity or strength. Two products that look similar can contain different substances or very different concentrations.
That is why PlusGBUK separates information about a drug’s known pharmacology from information about an unknown illicit product.
See our broader guide to drug testing and identification for more on these limits.
Dependence does not look the same across every drug
Alcohol, benzodiazepines, stimulants and dissociative drugs can all become difficult to stop, but the patterns are not identical.
Some substances produce prominent physical withdrawal. Others are more strongly associated with craving, fatigue, low mood, repeated use or compulsive behaviour.
That is why a single checklist rarely captures the full picture.
Our dependence and withdrawal hub explains the differences between physical dependence, tolerance, addiction, craving and withdrawal.
Drug combinations deserve separate attention
Interaction risk is often more important than the effect of either drug alone.
Cocaine and alcohol, for example, can produce cocaethylene. Benzodiazepines combined with opioids can deepen respiratory depression. Stimulants do not reliably “cancel out” sedatives.
See the drug interactions hub for substance-specific combination guides.
UK law varies by substance
Controlled drugs in the UK are divided into Classes A, B and C under the Misuse of Drugs Act framework. The class affects the maximum penalties for unauthorised possession, supply and production.
Legal classification is not a ranking of medical harm, and it should not be interpreted that way. Different substances are controlled under different schedules and classes for legal and regulatory reasons.
Our UK drug law hub explains classification, possession, supply and controlled-drug rules in more detail.
When substance use becomes a medical emergency
Call 999 if someone is unconscious, cannot be woken, is having a seizure, has severe breathing difficulty, collapses, develops severe chest pain, shows signs of stroke, or becomes dangerously overheated or confused.
Where the substance came from an illicit source, tell healthcare professionals what it was believed to be while making clear that its identity may be uncertain.
See our emergency help page for UK emergency information.
How PlusGBUK approaches substance information
We distinguish established evidence from uncertainty, medical treatment from illicit use, and chemical identity from product appearance.
We do not treat every person who uses a drug as dependent, and we do not minimise dependence where it is clearly present. We also avoid presenting a legal classification as though it automatically explains the medical risk profile.
The aim is practical, evidence-led information that helps readers understand what a substance does, where the real risks lie, and when professional or emergency help is appropriate.