Adolescence, schizophrenia and drug abuse: a window of vulnerability

Interaction of Brain-Derived Neurotrophic Factor with the Effects of Chronic Methamphetamine on Prepulse Inhibition in Mice Is Independent of Dopamine D3 Receptors

The aim of the present study was to gain a better understanding of the role of brain-derived neurotrophic factor (BDNF) and dopamine D3 receptors in the effects of chronic methamphetamine (METH) on prepulse inhibition (PPI), an endophenotype of psychosis. We compared the effect of a three-week adolescent METH treatment protocol on the regulation of PPI in wildtype mice, BDNF heterozygous mice (HET), D3 receptor knockout mice (D3KO), and double-mutant mice (DM) with both BDNF heterozygosity and D3 receptor knockout. Chronic METH induced disruption of PPI regulation in male mice with BDNF haploinsufficiency (HET and DM), independent of D3 receptor knockout. Specifically, these mice showed reduced baseline PPI, as well as attenuated disruption of PPI induced by acute treatment with the dopamine receptor agonist, apomorphine (APO), or the glutamate NMDA receptor antagonist, MK-801. In contrast, there were no effects of BDNF heterozygosity or D3 knockout on PPI regulation in female mice. Chronic METH pretreatment induced the expected locomotor hyperactivity sensitisation, where female HET and DM mice also showed endogenous sensitisation. Differential sex-specific effects of genotype and METH pretreatment were observed on dopamine receptor and dopamine transporter gene expression in the striatum and frontal cortex. Taken together, these results show a significant involvement of BDNF in the long-term effects of METH on PPI, particularly in male mice, but these effects appear independent of D3 receptors. The role of this receptor in psychosis endophenotypes therefore remains unclear.

Developmental influences on symptom expression in antipsychotic-naïve first-episode psychosis

BACKGROUND

The neurodevelopmental model of psychosis was established over 30 years ago; however, the developmental influence on psychotic symptom expression - how age affects clinical presentation in first-episode psychosis - has not been thoroughly investigated.

METHODS

Using generalized additive modeling, which allows for linear and non-linear functional forms of age-related change, we leveraged symptom data from a large sample of antipsychotic-naïve individuals with first-episode psychosis (N = 340, 12-40 years, 1-12 visits), collected at the University of Pittsburgh from 1990 to 2017. We examined relationships between age and severity of perceptual and non-perceptual positive symptoms and negative symptoms. We tested for age-associated effects on change in positive or negative symptom severity following baseline assessment and explored the time-varying relationship between perceptual and non-perceptual positive symptoms across adolescent development.

RESULTS

Perceptual positive symptom severity significantly decreased with increasing age (F = 7.0, p = 0.0007; q = 0.003) while non-perceptual positive symptom severity increased with age (F = 4.1, p = 0.01, q = 0.02). Anhedonia severity increased with increasing age (F = 6.7, p = 0.00035; q = 0.0003), while flat affect decreased in severity with increased age (F = 9.8, p = 0.002; q = 0.006). Findings remained significant when parental SES, IQ, and illness duration were included as covariates. There were no developmental effects on change in positive or negative symptom severity (all p > 0.25). Beginning at age 18, there was a statistically significant association between severity of non-perceptual and perceptual symptoms. This relationship increased in strength throughout adulthood.

CONCLUSIONS

These findings suggest that as maturation proceeds, perceptual symptoms attenuate while non-perceptual symptoms are enhanced. Findings underscore how pathological brain-behavior relationships vary as a function of development.

Post-pubertal Difference in Nigral Dopaminergic Cells Firing in the Schizophrenia Model Prepared by Perinatal Challenges of a Cytokine, EGF

Schizophrenia in humans typically develops during and after adolescence; however, the biological underpinning for the specificity of this onset time window remains to be determined. In the present study, we investigated this knowledge gap using our own animal model for schizophrenia. Rodents and monkeys challenged with a cytokine, epidermal growth factor (EGF), as neonates are known to exhibit various behavioral and cognitive abnormalities at the post-pubertal stage. We used the EGF-challenged mice as an animal model for schizophrenia to evaluate the electrophysiological impact of this modeling on nigral dopamine neurons before and after puberty. In vivo single unit recording revealed that the burst firing of putative dopamine neurons in substantia nigra pars compacta was significantly higher in the post-pubertal stage of the EGF model than in that of control mice; in contrast, this difference was not observed in the pre-pubertal stage. The increase in burst firing was accompanied by a decline in Ca²⁺-activated K⁺ (I_SK) currents, which influence the firing pattern of dopamine neurons. In vivo local application of the SK channel blocker apamin (80 μM) to the substantia nigra was less effective at increasing burst firing in the EGF model than in control mice, suggesting the pathologic role of the I_SK decrease in this model. Thus, these results suggest that the aberrant post-pubertal hyperactivity of midbrain dopaminergic neurons is associated with the temporal specificity of the behavioral deficit of this model, and support the hypothesis that this dopaminergic aberration could be implicated in the adolescent onset of schizophrenia.

Demographic, clinical and social characteristics of forensic patients diagnosed with schizophrenia at the Free State Psychiatric Complex, Bloemfontein, South Africa

Schizophrenia, prevalent in forensic mental health settings, is chronic and devastating, with a generally unfavourable course and prognosis. The aim of this study was to determine the demographic, clinical and social characteristics of forensic patients diagnosed with schizophrenia at the Free State Psychiatric Complex. A data collection form was used to gather information from the clinical records of patients diagnosed with schizophrenia between 1 January 2011 and 31 December 2015. The majority of the 110 participants were young male adults aged between 18 and 35 years with a low educational level. Cognitive impairment and positive symptoms were the most prominent clinical features. Aggressive and violent behaviour was notably prevalent. The majority of our sample had committed crimes against humans, while fewer had committed other types of crimes. It was concluded that causal factors included young adulthood, male gender, substance abuse, a poor social support system and lower educational level.

Pubertal Status and Age are Differentially Associated with Inflammatory Biomarkers in Female and Male Adolescents

A better understanding of the maturational correlates of inflammatory activity during adolescence is needed to more appropriately study both normal and abnormal development. Inflammation is the immune system's first response to infection, injury, or psychological stress, and it has been shown to be elevated in individuals with both physical and psychological conditions. This study examined unique associations between (1) pubertal status and inflammatory biomarkers, and (2) age and inflammatory biomarkers, and whether these relationships differed by sex in a diverse sample of 155 adolescents (54.2% female, 45.8% male; M_age = 16.22) from a northeastern city in the US. A more advanced pubertal status was uniquely associated with lower levels of tumor necrosis factor alpha (TNF-α) and interleukin-8 (IL-8). Chronological age was uniquely associated with lower IL-8 levels. The association between pubertal status and C-reactive protein (CRP) levels differed by sex: more mature females had higher CRP, whereas pubertal status and CRP were not significantly associated in males. These findings highlight an important relation between pubertal development and inflammatory activity during adolescence.

Social vs. environmental stress models of depression from a behavioural and neurochemical approach

Major depression is a mental disorder often preceded by exposure to chronic stress or stressful life events. Recently, animal models based on social conflict such as chronic social defeat stress (CSDS) are proposed to be more relevant to stress-induced human psychopathology compared to environmental models like the chronic mild stress (CMS). However, while CMS reproduces specifically core depressive symptoms such as anhedonia and helplessness, CSDS studies rely on the analysis of stress-induced social avoidance, addressing different neuropsychiatric disorders. Here, we study comparatively the two models from a behavioural and neurochemical approach and their possible relevance to human depression. Mice (C57BL/6) were exposed to CMS or CSDS for six weeks and ten days. Anhedonia was periodically evaluated. A battery of test applied during the fourth week after the stress procedure included motor activity, memory, anxiety, social interaction and helplessness. Subsequently, we examined glutamate, GABA, 5-HT and dopamine levels in the prefrontal cortex, hippocampus and brainstem. CMS induced a clear depressive-like profile including anhedonia, helplessness and memory impairment. CSDS induced anhedonia, hyperactivity, anxiety and social avoidance, signs also common to anxiety and posttraumatic stress disorders. While both models disrupted the excitatory inhibitory balance in the prefrontal cortex, CMS altered importantly this balance in the brainstem. Moreover, CSDS decreased dopamine in the prefrontal cortex and brainstem. We suggests that while depressive-like behaviours might be associated to altered aminoacid neurotransmission in cortical and brain stem areas, CSDS induced anxiety behaviours might be linked to specific alteration of dopaminergic pathways involved in rewarding processes.

Antipsychotic treatment of adolescent dual diagnosis patients

BACKGROUND

A diagnosis of schizophrenia requires development of a pharmacotherapy regimen that balances many factors in the therapeutic decision-making process. Patient age and the presence or absence of comorbid chemical dependency represent two factors. Comorbid chemical dependency can have a profound impact on the successful treatment of schizophrenia, making patients with dual diagnoses of schizophrenia and chemical dependence a uniquely challenging population. There is little information regarding treatment of schizophrenia and chemical dependence in the pediatric population. Existing data from pediatric and adult populations may facilitate a well-guided and knowledgeable approach to treating pediatric dual diagnosis patients.

METHODS

A review of the literature for medication trials evaluating antipsychotic medication used to treat schizophrenia in childhood and adolescence as well as antipsychotic use in the treatment of the dual diagnoses of schizophrenia and chemical dependence was done. Databases for Ovid MEDLINE, PubMed, and PsycInfo were searched using the terms "addiction," "adolescence," "childhood," "dual diagnosis," "schizophrenia," and "substance abuse." Results were limited to English-language articles.

RESULTS

Seven articles were identified related to psychotic disorders and substance abuse in pediatric populations. Psychosis measurement instruments included the Brief Psychiatric Rating Scale, Positive and Negative Syndrome Scale, and Clinical Global Impression. Mean improvements were insignificant in most cases. Medication trials included clozapine, olanzapine, risperidone, and molindone. Trial safety concerns included metabolic effects, increased prolactin levels, and akathisia. One study with random assignment to olanzapine was discontinued early because of substantial weight gain without evidence of superior efficacy. Clozapine treatment was associated with more adverse drug events.

CONCLUSION

There is a great need for more research and use of available data to develop safe and effective treatment guidelines for childhood and adolescent dual diagnosis patients. When appropriate decisions are made regarding treatment of patients with comorbid schizophrenia and chemical dependence, both conditions may benefit with increased remission.

Substance use disorder among people with first-episode psychosis: a systematic review of course and treatment

OBJECTIVE

People experiencing a first episode of psychosis frequently have co-occurring substance use disorders, usually involving alcohol and cannabis, which put them at risk for prolonged psychosis, psychotic relapse, and other adverse outcomes. Yet few studies of first-episode psychosis have addressed the course of substance use disorders and the response to specialized substance abuse treatments.

METHODS

The authors searched MEDLINE, PsycINFO, and other medical databases for English-language articles published between 1990 and 2009. Included studies addressed two research questions. First, do some clients become abstinent after a first episode of psychosis without specialized substance abuse treatments? Second, for clients who continue to use substances after a first episode of psychosis, does the addition of specialized substance abuse treatment enhance outcomes?

RESULTS

Nine studies without specialized substance abuse treatment and five with specialized substance abuse treatment assessed the course of substance use (primarily cannabis and alcohol) after a first episode of psychosis. Many clients (approximately half) became abstinent or significantly reduced their alcohol and drug use after a first episode of psychosis. The few available studies of specialized substance abuse treatments did not find better rates of abstinence or reduction.

CONCLUSIONS

Experience, education, treatment, or other factors led many clients to curtail their substance use disorders after a first episode of psychosis. Specialized interventions for others need to be developed and tested.

Diffusion tensor imaging in the early phase of schizophrenia: what have we learned?

The dysconnectivity model suggests that disturbed integration of neural communication is central to schizophrenia. The integrity of macro-structural brain circuits can be examined with diffusion tensor imaging (DTI), an MRI application sensitive to microstructural abnormalities of brain white matter. DTI studies in first-episode schizophrenia patients and individuals at high-risk of psychosis can provide insight into the role of structural dysconnectivity in the liability, onset and early course of psychosis. This review discusses (i) views on the role of white matter abnormalities in schizophrenia, (ii) DTI and its application in schizophrenia, (iii) DTI findings in first-episode patients and subjects at high-risk of psychosis; their timing, anatomical location and early course, (iv) the hypothesized underlying pathological substrate and possible causes of DTI white matter alterations, including effects of adolescent cannabis use, and (v) some methodological issues and future recommendations. In summary, there is evidence that DTI abnormalities convey a liability for psychosis and additional abnormalities occur around onset of psychosis. However, findings in first-episode patients are less robust than in chronic patients, and progression of disturbances may occur in the early course of poor-outcome patients. In addition, acceleration of the normal aging process may occur. Adolescent cannabis use has specific effects on DTI measures. An unresolved issue is the underlying pathology of DTI abnormalities, and combining DTI with other MRI indices can provide more insight. More research is needed on which genetic and environmental factors play a role in the variability of current results.

Toward a neurobiology of delusions

Delusions are the false and often incorrigible beliefs that can cause severe suffering in mental illness. We cannot yet explain them in terms of underlying neurobiological abnormalities. However, by drawing on recent advances in the biological, computational and psychological processes of reinforcement learning, memory, and perception it may be feasible to account for delusions in terms of cognition and brain function. The account focuses on a particular parameter, prediction error--the mismatch between expectation and experience--that provides a computational mechanism common to cortical hierarchies, fronto-striatal circuits and the amygdala as well as parietal cortices. We suggest that delusions result from aberrations in how brain circuits specify hierarchical predictions, and how they compute and respond to prediction errors. Defects in these fundamental brain mechanisms can vitiate perception, memory, bodily agency and social learning such that individuals with delusions experience an internal and external world that healthy individuals would find difficult to comprehend. The present model attempts to provide a framework through which we can build a mechanistic and translational understanding of these puzzling symptoms.

Temporal relationship of first-episode non-affective psychosis with cannabis use: a clinical verification of an epidemiological hypothesis

BACKGROUND

We analyzed the association of age at onset of psychosis treatment (AOPT) with having a history of cannabis use in patients with a first episode of non-affective psychosis. We also investigated the impact on the AOPT of exposure to cannabis in adolescence, compared with young adulthood, and of the additional exposure to cocaine.

METHOD

We recruited 112 consecutive patients (66 men and 46 women; age range, 18-57years) with a first psychotic episode. The composite international diagnostic interview (CIDI) was used to assess drug use and to define the age at onset of heaviest use (AOHU) of a drug, defined as the age when drug was used the most for each patient. The effect of cannabis and cocaine AOHU on AOPT was explored through Kruskal-Wallis and Mann-Whitney tests, and logistic regression. Sex-adjusted cumulative hazard curves and Cox regression models were used to compare the AOPT of patients with and without a history of cannabis use, or associated cocaine use.

RESULTS

We found that the AOPT was significantly associated with the use of cannabis, independently of sex, use of cocaine, tobacco smoking or excessive alcohol consumption. There was a dose-response relationship between cannabis AOHU and AOPT: the earlier the AOHU the earlier the AOPT. Hazard curves showed that patients with a history of cannabis use had a higher hazard of having a first-episode psychosis than the rest of the patients (sex-adjusted log-rank chi(2)=23.43, df=1, p<0.001). Their respective median AOPT (25th, 75th percentiles) were 23.5 (21, 28) and 33.5years (27, 45) (for log-transformed AOPT, t=5.6, df=110, p<0.001). The sex-adjusted hazard ratio of psychosis onset comparing both groups was 2.66 (95% CI, 1.74-4.05).

CONCLUSIONS

Our results are in favor of a catalytic role for cannabis use in the onset of psychosis.

Long-term behavioral consequences of prenatal MDMA exposure

The current study sought to determine whether prenatal 3,4-methylenedioxy-N-methamphetamine (MDMA) exposure from E14-20 in the rat resulted in behavioral sequelae in adult offspring. Prenatal MDMA exposure results in increased dopaminergic fiber density in the prefrontal cortex, striatum and nucleus accumbens of young rats. Since these areas are critical in response to novelty, reward, attention and locomotor activity, we hypothesized that prenatal MDMA exposure would produce significant changes in the performance of tasks that examine such behaviors in adult rats. Adult rats prenatally exposed to MDMA exhibited greater activity and spent more time in the center during a novel open field test as compared to controls. This increased activity was not reflected in normal home cage activity. Prenatal exposure to MDMA did not affect feeding or food reward. It did not alter cocaine self-administration behaviors, nor did it have an effect on the locomotor response to amphetamine challenge. Finally, while prenatal MDMA did not affect performance in the radial arm maze or the Morris water maze (MWM), these animals demonstrated altered performance in a cued MWM paradigm. Prenatal MDMA exposure resulted in perseverative attendance to a hanging cue when the platform in the MWM was removed as compared to controls. Together, these data demonstrate that prenatal exposure to MDMA results in a behavioral phenotype in adult rats characterized by reduced anxiety, a heightened response to novelty, and "hyperattentiveness" to environmental cues during spatial learning.

Signs and symptoms in the pre-psychotic phase: description and implications for diagnostic trajectories

BACKGROUND

Few studies have examined the underlying factor structure of signs and symptoms occurring before the first psychotic episode. Our objective was to determine whether factors derived from early signs and symptoms are differentially associated with non-affective versus affective psychosis.

METHOD

A principal components factor analysis was performed on early signs and symptoms reported by 128 individuals with first-episode psychosis. Factor scores were examined for their associations with duration of untreated illness, drug abuse prior to onset of psychosis, and diagnosis (schizophrenia versus affective psychosis).

RESULTS

Of the 27 early signs and symptoms reported by patients, depression and anxiety were the most frequent. Five factors were identified based on these early signs and symptoms: depression, disorganization/mania, positive symptoms, negative symptoms and social withdrawal. Longer duration of untreated illness was associated with higher levels of depression and social withdrawal. Individuals with a history of drug abuse prior to the onset of psychosis scored higher on pre-psychotic depression and negative symptoms. The two mood-related factors, depression and disorganization/mania, distinguished the eventual first-episode diagnosis of affective psychosis from schizophrenia. Individuals with affective psychosis were also more likely to have a 'mood-related' sign and symptom as their first psychiatric change than individuals later diagnosed with schizophrenia.

CONCLUSIONS

Factors derived from early signs and symptoms reported by a full diagnostic spectrum sample of psychosis can have implications for future diagnostic trajectories. The findings are a step forward in the process of understanding and characterizing clinically important phenomena to be observed prior to the onset of psychosis.

Adolescent maturation of cocaine-sensitive neural mechanisms

Both clinical and animal studies have shown that adolescents undergo a late maturation of the central nervous system, which may underlie adolescent typical behaviors. In particular, decreased behavioral response to cocaine has been found in adolescents as compared to adults. In the present study, cocaine was used as a tool to explore adolescent brain maturation. Juvenile (postnatal day (P) 27), adolescent (P37), and adult (P90) male Sprague-Dawley rats were treated acutely with cocaine (750 microg/kg/injection x 2, i.v.), and c-fos mRNA expression, a marker of neuronal activation, was evaluated by in situ hybridization. Cocaine-induced c-fos mRNA was similar across ages in the dorsal caudate putamen (CPu), nucleus accumbens, and lateral bed nucleus of the stria terminalis. In contrast, there was a diminished response in juvenile/adolescent ventral CPu and in juvenile central nucleus of the amygdala, and an increased response in juvenile/adolescent cortex. Further studies evaluated the mechanism of the late maturation of cocaine response in ventral CPu. No significant age differences were observed in regional dopamine (DA) transporter binding. Although striatal DA content was significantly reduced at P27 as compared to adult, there was no difference between dorsal and ventral subregions. In contrast, basal- and cocaine-induced extracellular DA overflow, as measured by in vivo microdialysis, was lower in juvenile ventral CPu than in the adults. This age difference was not observed in dorsal CPu. These findings suggest that impulse activity in DA afferents to ventral CPu is immature in adolescents. In conclusion, the present study showed that cocaine-sensitive neuronal circuits continue to mature during adolescence.

Is cannabis use a contributory cause of psychosis?

OBJECTIVE

To assess whether cannabis use in adolescence and young adulthood is a contributory cause of schizophreniform psychosis in that it may precipitate psychosis in vulnerable individuals.

METHOD

We reviewed longitudinal studies of adolescents and young adults that examined the relations between self-reported cannabis use and the risk of diagnosis with a psychosis or of reporting psychotic symptoms. We also reviewed studies that controlled for potential confounders, such as other forms of drug use and personal characteristics that predict an increased risk of psychosis. We assessed evidence for the biological plausibility of a contributory causal relation.

RESULTS

Evidence from 6 longitudinal studies in 5 countries shows that regular cannabis use predicts an increased risk of a schizophrenia diagnosis or of reporting symptoms of psychosis. These relations persisted after controlling for confounding variables, such as personal characteristics and other drug use. The relation did not seem to be a result of cannabis use to self-medicate symptoms of psychosis. A contributory causal relation is biologically plausible because psychotic disorders involve disturbances in the dopamine neurotransmitter systems with which the cannabinoid system interacts, as demonstrated by animal studies and one human provocation study.

CONCLUSION

It is most plausible that cannabis use precipitates schizophrenia in individuals who are vulnerable because of a personal or family history of schizophrenia.

Anhedonia in schizophrenia

This review highlights key issues and recent progress in understanding the epidemiology, phenomenology, etiology, and treatment of anhedonia in schizophrenia. A reduced pleasure capacity has been recognized as an important feature of the illness since the time of Kraepelin and Bleuler. However, it remains poorly understood for many reasons, including the phenotypic heterogeneity of schizophrenia, the multidimensionality and multifactorial etiology of anhedonia, and the difficulties inherent in the scientific analysis of subjective emotional experiences. We do know that anhedonia is common in schizophrenia, that it has significant negative consequences, and that current treatments are insufficient. Better assessment tools, greater understanding of biological and psychosocial mechanisms, and novel pharmacologic and psychosocial interventions are sorely needed. Anhedonia has received increasing attention in recent years, and there is optimism that the new Measurement and Treatment Research to Improve Cognition in Schizophrenia (MATRICS) initiative on negative symptoms will catalyze rapid progress in the near future.

Substance abuse in patients with schizophrenia

The comorbidity of schizophrenia and substance abuse has attracted increasing attention in the past years, with multiple potential links, including genetic vulnerability, neurobiological aspects, side effects of medications, and psychosocial factors being under discussion. The link between the use of substances and the development of psychoses is demonstrated by the high prevalence of substance abuse in schizophrenia. Apart from alcohol misuse, substances commonly abused in this patient group include nicotine, cocaine, and cannabis. In particular, heavy cannabis abuse has been reported to be a stressor eliciting relapse in schizophrenic patients. In general, substance use in psychosis is associated with poorer outcomes, including increased psychotic symptoms and poorer treatment compliance. Since both disorders have been observed to be closely interdependent, a particular treatment for schizophrenic patients with comorbidity of substance abuse is needed in order to provide more effective care. In this article, we discuss various potential modes of interaction and interdependence, and the possibility of embarking on new therapeutic paths for treating this particular population.

Neuroleptic dysphoria: revisiting the concept 50 years later

OBJECTIVE

To review the concept of neuroleptic dysphoria, its historical development and the current state of the art.

METHOD

This paper is based on extensive but selective literature review and also draws on our extensive clinical and research experiences.

RESULTS

Although the construct of neuroleptic dysphoria was recognized shortly following the introduction of the first antipsychotic, chlorpromazine, it took several years for the concept to receive adequate research and clinical attention. Without having direct evidence to link neuroleptic dysphoria to dopamine, it was generally understood that dopamine played a significant role in its genesis. In recent neuroimaging studies and dopamine depletion strategies, the role of dopamine in the genesis of neuroleptic dysphoria has been directly confirmed.

CONCLUSION

Neuroleptic dysphoria is a valid construct, which has significant implications for treatment and outcome. It is now clear that it relates to dopamine activities in the nigrostriatal complex. Recent research has also raised the issue of whether neuroleptic dysphoria is a variant of extrapyramidal symptoms. Meanwhile, the role of dopamine in both the genesis of neuroleptic dysphoria and addictive behaviour has raised the issue of both conditions being different facets of the schizophrenic disease process. The recent interface of addiction and psychiatry research may have opened a new science: the science of subjective tolerability disorders.