Reconciling 'the new epidemiology' with an evolutionary genetic basis for schizophrenia

Systems psychopharmacology: A network approach to developing novel therapies

The multifactorial origin of most chronic disorders of the brain, including schizophrenia, has been well accepted. Consequently, pharmacotherapy would require multi-targeted strategies. This contrasts to the majority of drug therapies used until now, addressing more or less specifically only one target molecule. Nevertheless, quite some searches for multiple molecular targets specific for mental disorders have been undertaken. For example, genome-wide association studies have been conducted to discover new target genes of disease. Unfortunately, these attempts have not fulfilled the great hopes they have started with. Polypharmacology and network pharmacology approaches of drug treatment endeavor to abandon the one-drug one-target thinking. To this end, most approaches set out to investigate network topologies searching for modules, endowed with "important" nodes, such as "hubs" or "bottlenecks", encompassing features of disease networks, and being useful as tentative targets of drug therapies. This kind of research appears to be very promising. However, blocking or inhibiting "important" targets may easily result in destruction of network integrity. Therefore, it is suggested here to study functions of nodes with lower centrality for more subtle impact on network behavior. Targeting multiple nodes with low impact on network integrity by drugs with multiple activities ("dirty drugs") or by several drugs, simultaneously, avoids to disrupt network integrity and may reset deviant dynamics of disease. Natural products typically display multi target functions and therefore could help to identify useful biological targets. Hence, future efforts should consider to combine drug-target networks with target-disease networks using mathematical (graph theoretical) tools, which could help to develop new therapeutic strategies in long-term psychiatric disorders.

Can the new epidemiology of schizophrenia help elucidate its causation?

The supposed universality of the incidence and prevalence of schizophrenia has been seriously challenged. It is now widely accepted that the life-time prevalence and incidence of this disorder vary considerably in time and place. As a result, there has been renewed interest in environmental causation of schizophrenia. There are few extant formulations that have successfully integrated the available new evidence into a coherent theory for its causation. The outgroup intolerance hypothesis is an attempt to integrate this evidence. It proposes that schizophrenia is the result of a mismatch between the social brain as shaped by evolution and the new social conditions of the post-neolithic. The hypothesis can provide an explanation for (i) the higher risk to migrants, (ii) the ethnic density phenomenon, (iii) the increased risk to individuals who have grown up in cities and (iv) the putative low risk in hunter-gatherer societies. Evidence is presented from a range of disciplines and sources including epidemiology, psychopathology, social psychology and clinical trials in support of this hypothesis. A range of testable predictions follow from the hypothesis.

Joining the dots: neurobiological links in a functional analysis of depression

Depression is one of the major contributors to the Total Disease Burden and afflicts about one-sixth of Western populations. One of the most effective treatments for depression focuses upon analysis of causal chains in overt behaviour, but does not include brain-related phenomena as steps along these causal pathways. Recent research findings regarding the neurobiological concomitants of depressive behaviour suggest a sequence of structural and functional alterations to the brain which may also produce a beneficial outcome for the depressed individual--that of adaptive withdrawal from uncontrollable aversive stressors. Linking these brain-based explanations to models of observable contingencies for depressive behaviour can provide a comprehensive explanation of how depressive behaviour occurs and why it persists in many patients.

Is depression "evolutionary" or just "adaptive"? A comment

Some recent explanations of depression have suggested that it may be "evolutionary" in that there are advantages to the depressed individual which arise from some aspects of depressive symptomatology. While the depressive behaviour of withdrawal from the adverse environment may provide some immediate benefits to the depressed individual, thus making it potentially "adaptive" in the short-term, this does not fit the biological definition of "evolutionary". In fact, depression does not meet two of the three required criteria from natural selection in order to be evolutionary. Therefore, while some depressive behaviour may be advantageous for the depressed individual, and is therefore "adaptive" in an immediate sense, it cannot be accurately described as "evolutionary". Implications for research and clinical practice are discussed.