New psychoactive substances (NPS) are a heterogeneous group of substances. They are associated with a number of health and social harms on an individual and societal level. NPS toxicity and dependence syndromes are recognised in primary care, emergency departments, psychiatric inpatient and community care settings. One pragmatic classification system is to divide NPS into one of four groups: synthetic stimulants, synthetic cannabinoids, synthetic hallucinogens and synthetic depressants (which include synthetic opioids and benzodiazepines). We review these four classes of NPS, including their chemical structures, mechanism of action, modes of use, intended intoxicant effects, and their associated physical and mental health harms. The current challenges faced by laboratory testing for NPS are also explored, in the context of the diverse range of NPS currently available, rate of production and emergence of new substances, the different formulations, and methods of acquisition and distribution.

Bupropion has been used as an antidepressant for over 20 years, though its licence for such use varies and it is typically a third- or fourth-line agent. It has a unique pharmacology, inhibiting the reuptake of noradrenaline and dopamine, potentially providing pharmacological augmentation to more common antidepressants such as selective serotonergic reuptake inhibitors (SSRIs). This systematic review and meta-analysis identified 51 studies, dividing into four categories: bupropion as a sole antidepressant, bupropion coprescribed with another antidepressant, bupropion in ‘other’ populations (e.g. bipolar depression, elderly populations) and primary evaluation of side effects. Methodologically more robust trials support the superiority of bupropion over placebo, and most head-to-head antidepressant trials showed an equivalent effectiveness, though some of these are hindered by a lack of a placebo arm. Most work on the coprescribing of bupropion with another antidepressant supports an additional effect, though many are open-label trials. Several large multi-medication trials, most notably STAR*D, also support a therapeutic role for bupropion; in general, it demonstrated similar effectiveness to other medications, though this literature highlights the generally low response rates in refractory cohorts. Effectiveness has been shown in ‘other’ populations, though there is an overall dearth of research. Bupropion is generally well tolerated, it has very low rates of sexual dysfunction, and is more likely to cause weight loss than gain. Our findings support the use of bupropion as a sole or coprescribed antidepressant, particularly if weight gain or sexual dysfunction are, or are likely to be, significant problems. However there are notable gaps in the literature, including less information on treatment naïve and first presentation depression, particularly when one considers the ever-reducing rates of response in more refractory illness. There are some data to support bupropion targeting specific symptoms, but insufficient information to reliably inform such prescribing, and it remains uncertain whether bupropion pharmacodynamically truly augments other drugs.

Depression is a potentially life-threatening disorder affecting millions of people across the globe. It is a huge burden to both the individual and society, costing over £9 billion in 2000 alone: the World Health Organisation (WHO) cited it as the third leading cause of global disability in 2004 (first in the developed world), and project it will be the leading cause by 2030. The serendipitous discovery of antidepressants has revolutionized both our understanding and management of depression: however, their efficacy in the treatment of depression has long been debated and recently been brought very much into the public limelight by a controversial publication by Kirsch, in which the role of placebo response in antidepressant efficacy trials is highlighted. Whilst antidepressants offer benefits in both the short and long term, important problems persist such as intolerability, delayed therapeutic onset, limited efficacy in milder depression and the existence of treatment-resistant depression.

Lithium has been used for the treatment of mood disorders for over 60 years, yet the exact mechanisms by which it exerts its therapeutic effects remain unclear. Two enzymatic chains or pathways emerge as targets for lithium: inositol monophosphatase within the phosphatidylinositol signalling pathway and the protein kinase glycogen synthase kinase 3. Lithium inhibits these enzymes through displacing the normal cofactor magnesium, a vital regulator of numerous signalling pathways. Here we provide an overview of evidence, supporting a role for the inhibition of glycogen synthase kinase 3 and inositol monophosphatase in the pharmacodynamic actions of lithium. We also explore how inhibition of these enzymes by lithium can lead to downstream effects of clinical relevance, both for mood disorders and neurodegenerative diseases. Establishing a better understanding of lithium’s mechanisms of action may allow the development of more effective and more tolerable pharmacological agents for the treatment of a range of mental illnesses, and provide clearer insight into the pathophysiology of such disorders.

The burden of depressive disorders and the frequent inadequacy of their current pharmacological treatments are well established. The anaesthetic and hallucinogenic drug ketamine has provoked much interest over the past decade or so as an extremely rapidly acting antidepressant that does not modify ‘classical’ monoaminergic receptors. Current evidence has shown several ways through which it might exert therapeutic antidepressant actions: blockade of glutamatergic NMDA receptors and relative upregulation of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) subtypes may alter cortical connectivity patterns; through intracellular changes in protein expression, including the proteins mammalian target of rapamycin (mTOR) and brain-derived neurotrophic factor (BDNF); and alteration of intracellular signalling cascades. The clinical evidence demonstrates rapid improvements in mood and suicidal thinking in most participants, although study numbers have generally been small and many trials are unblinded and methodologically weak. There is a small body of work to suggest ketamine might also augment electroconvulsive therapy and potentially have a role as a surgical anaesthetic in depressed patients. A major problem is that the effects of ketamine appear temporary, disappearing after days to weeks (although longer benefits have been sustained in some), and attempts to circumvent this through pharmacological augmentation have been disappointing thus far. These exciting data are providing new insights into neurobiological models of depression, and potentially opening up a new class of antidepressants, but there are significant practical and ethical issues about any future mainstream clinical role it might have.