Psychoactive drugs, by definition, cause mood states to change and fluctuate. Hence an important factor for drug-induced distress is mood instability. This is found with sedative drugs such as alcohol or cannabis, and stimulant drugs such as cocaine or methamphetamine [1,2,3,4,5,6]. Indeed, the main reason that psychoactive drugs are used recreationally is for their “positive” mood effects, such as feelings of relaxation and pleasure [4]. Novel psychoactive substances (NPS) such as mephedrone and spice cannabinoids are very similar in this regard [6,7,8,9]. Although one of the paradoxes of drug taking is that many of the apparent mood gains represent the reversal of unpleasant abstinence feelings. Nicotine is a prime example of this pattern [10,11,12], although it also occurs with other substances [4].

Psychoactive drugs can also produce undesirable mood state changes. For instance, recreational cannabis, whether herbal or spice, can lead to feelings of tension and suspiciousness [2,13]. Stimulants such as cocaine, methamphetamine and mephedrone can also lead to feelings of anxiety and paranoia [1,14,15]. The acute mood effects of all psychoactive drugs can be highly variable and may differ considerably between individuals. On alcohol some users become happy and jovial, while others become moody and aggressive, especially after excess levels of consumption [5,16,17]. In a similar way, Le Strat et al. [18] documented a wide range of responses to an acute dose of cannabis. Furthermore, those with positive initial mood reactions were most likely to become regular cannabis users, whereas those with negative or neutral mood reactions to cannabis tended not to persevere with its usage. Similar differences in mood response have also been empirically demonstrated with the methamphetamine derivative MDMA (3,4-methylenedioxymethamphetamine or “Ecstasy”). This drug is often described as the most euphoriant of all the recreational stimulants. Yet acute MDMA can release a wide range of feelings and cognitions-both positive and negative. Liechti et al. [19] found that an acute dose of MDMA in the laboratory led to significant increases in feelings of both introversion and extraversion, while feelings of happiness and depression were also significantly intensified. In a comprehensive review of the acute-dose MDMA mood literature, it was found that a wide range of positive and negative psychological material could be released/intensified [20]. For instance, psychotherapists who have incorporated MDMA into their therapy sessions have noted that the emergent psychological material can be difficult and stressful for the client to handle, although its release may also be important for potential therapeutic gains [20,21,22,23,24]. In positive environmental situations, the positive mood effects of MDMA predominate, whereas in neutral situations its mood effects can be more variable and less positive [14,15]. These adverse mood abreactions to MDMA can be more frequent than is commonly portrayed. In an article entitled: “Hug drug or thug drug”, Reid et al. [25] noted that MDMA often generated feelings of anger and aggression. Rugani et al. [26] noted that acute psychotic patients who had used MDMA for recreational purposes demonstrated heightened levels of hostility, physical violence, and verbal aggression than non-users. The authors noted that this finding “surely runs counter to the expected entactogenic effects of Ecstasy” (for further debate, see [27]).

In a large Internet study of mephedrone and MDMA users, the acute mood effects of each drug were broadly similar, although some intriguing differences in pharmacodynamic tolerance were apparent [9]. A mixture of positive and negative mood changes is also found with established recreational stimulants such as cocaine [28], and laboratory doses of methamphetamine [14,15]. The effects of high doses of amphetamine and cocaine can be very strong, with reports of a physical rush or hit. These high doses can lead to intensely negative moods, with very severe feelings of suspiciousness, or clinical paranoia. Spice cannabinoids can also have far stronger effects that herbal cannabis, in both positive and negative ways [29]. The more extreme mood reactions of the more powerful drugs can lead to changeable and unpredictable patterns of behavior. However, these abreactions can occur with any psychoactive drug, irrespective of whether they are established or novel.