It is well known that mental disorders are accompanied by multiple comorbidities, but substance misuse is particularly common [1]. Many clinicians feel that substance misuse may be explained in some cases as a form of self-medication to improve psychopathology (depression, anhedonia, and negative symptoms) or to ameliorate the side effects of psychopharmacological treatment. Indeed, the cooccurrence between mental disorders and psychoactive substances misuse often leads to a more pernicious and difficult to treat course of illness, in terms of possible earlier age of onset, frequency and length of episodes, and diminished treatment compliance [2, 3]. Moreover, there is substantial evidence that substance misuse is a major risk factor for violence and aggression in patients with major mental disorders [4]. To get an idea of the problem dimension as a health issue, in 2010 mental and substance use disorders accounted for 183.9 million disability-adjusted life years (DALYs) or 7.4% of all DALYs worldwide. Thus, considered together, mental and substance use disorders were the leading cause of years lived with disability (YLDs) worldwide [5]. The long-term consequences of increased reactivity (sensitisation) to episodes and substances misuse and their cross-sensitisation to each other may have a number of important implications for clinical therapeutics [2, 6]. The potential cross-sensitisation among stressors, episodes, and substances misuse raises the spectre of an adverse positive feedback mechanism in each domain of illness vulnerability, with recurrences of each not only increasing responsivity to itself, but also increasing responsivity to the others [2].

Recently, beyond “classic” substances of abuse, it seems that novel (new) psychoactive substances (NPS) are determining a further sanitary issue of growing importance, especially in relation to the fast-moving and potentially unlimited nature of their online market [7]. The term “novel psychoactive substances” (NPS) has been legally defined by European Union as a new narcotic or psychotropic drug, in pure form or in a preparation, that is not scheduled under the Single Convention on Narcotic Drugs of 1961 or the Convention on Psychotropic Substances of 1971, but may pose a public health threat comparable to that posed by substances listed in those conventions (Council of the European Union decision 2005/387/JHA) [8]. NPS are often almost unknown to health professionals, mainly due to the lack of evidence-based sources of information [9]. Since 1997, more than 200 novel psychoactive compounds have been reported; out of these, 41 were reported in 2010, 60 in 2011, and 57 in 2012 [7]. These substances are most often synthesized in underground laboratories, simply modifying the molecular structure of controlled drugs, hence raising further concerns in terms of the presence of contaminating agents [8]. The World Wide Web has emerged as a primary source of information about drugs in general and NPS in particular. Drug users can obtain information through online forums, chat rooms, and blogs and find out about new products. They can also communicate with other users about their experiences, the effects of the substances, and the recommended sources and routes of delivery. This may be an issue of concern if one considers that an estimated 61% of young European people aged between 15 and 24 years typically quote the Internet as a potential source of information on drugs [10]. The number of online shops offering to supply with NPS customers residing in European countries increased from 170 in January 2010 to 314 in January 2011 and 693 in January 2012 [7]. The possibility of purchasing NPS from web sites makes these drugs very easily available to vulnerable individuals, including children and adolescents. Vulnerable consumers are targeted by aggressive marketing strategies (attractive names, colourful packaging, and free samples to test); NPS appear to be mostly unregulated, and this may facilitate their popularity as well as the users' perception of risks associated with consumption. The idea that legality can equate with safety still remains well grounded amongst some recreational users [9].

Thus, the focus on novel psychoactive substances, peculiarly in youths, has become a diffuse topic of discussion in scientific literature, underlining a growing interest for this widespread phenomenon. However, still few epidemiological data about NPS diffusion exists. Recent data by European Monitoring Centre on Drugs and Drug Addiction (EMCDDA) highlights that small percentages of tested youths have experienced NPS (around 5%), most of them obtaining drugs from friends or at parties, rather than online [11]. A UK-based research found out that almost one-third of a sample of students (446) had tried NPS at least once in their life. A Polish epidemiological study on 14511 secondary school pupils and university students has registered NPS use rate of 4.49% and 1.83%, respectively [12]. The psychoactive substances abuse issue has been recently emphasized by researchers from all over the world: Madruga et al. have gathered information on a sample of 761 Brazilians aged from 14 to 19 years old; more than half of interviewed adolescents are regular alcohol users and one out of ten is an abuser and/or dependent, while nearly 3% has used an illicit substance in the twelve months before questionnaire administration [13]. Famuyiwa and colleagues supply epidemiologic data on 4286 school pupils (mean age 15.2 years) from Lagos, Nigeria, finding that 61.8% of respondents have used one or more psychoactive substances in their lifetime [14]. Currie reports results on Salvia divinorum consumption from Canada's Youth Smoking Survey (sample of 42179 Canadian adolescents aged 12–17 years), evidencing that 6.2% of the subjects has used the substance at least once in their life [15]. Kelly et al. have performed a field-based survey of 1740 patrons at nightlife venues in New York City. Within the sample, 8.2% reported use of synthetic cannabinoids and 1.1% reported use of mephedrone; the findings suggest that the use of synthetic cannabinoids and mephedrone among US nightlife scenes may remain relatively low in comparison with European nightlife scenes [16]. A recent study by Bruno et al. among 693 regular ecstasy users (REU) in Australia has evidenced that more than one quarter (28%) of REU have used a new psychoactive substance in the past six months, most commonly from the stimulant class (20%, typically mephedrone 17%) rather than from the psychedelic class (13%) [17]. These behaviours and patterns of use are encouraged by the increasing phenomenon of binge drinking, widely diffused in Europe and North America [18–20].

To the best of our knowledge, no current data exist about the use of NPS among psychiatric patients. This is the first study aiming to assess both the presence and the nature of NPS misuse in a population of Italian young adults in comparison with a psychiatry patient sample.