Platelet [3H]paroxetine binding in patients with OCD-related disorders

A long and winding road: My personal journey to oxytocin with no return

The present paper is the personal narration of the author reviewing her scientific pathways that led her toward the study of oxytocin. My work began with a pioneering study showing a decreased number of the serotonin transporter proteins in romantic lovers. This unexpected finding promoted my interest in the neurobiology of human emotions and feelings, and significantly shifted my research focus from diseases to physiological states that underlie "love." During this time increasing experimental data broadened the spectrum of activities of oxytocin from female functions, such as parturition and lactation, to modulation of the stress and immune system. The literature also began to reveal an important role for oxytocin in a sense of safety and wellbeing, processes that are critical to both love and survival. I suggest here that future studies should disentangle different emerging questions regarding the exact role of oxytocin within human nature, as well as its possible therapeutic applications in different physiological conditions and pathological states. Understanding these, in turn, holds the potential to improve the lives of both individuals and societies.

Pharmacotherapeutic Strategies and New Targets in OCD

Effective pharmacological and psychotherapeutic treatments are well established for obsessive-compulsive disorder (OCD). Serotonin reuptake inhibitors (SRIs) are first-line treatment and are of benefit to about half of patients. Augmentation of SRI treatment with low-dose neuroleptics is an evidence-based second-line strategy. Specialty psychotherapy is also used as both first-line and second-line treatment and can benefit many. However, a substantial number of patients do not respond to these treatments. New alternatives are urgently needed. This review summarizes evidence for these established pharmacotherapeutic strategies, and for others that have been investigated in refractory disease but are not supported by the same level of evidence. We focus on three neurotransmitter systems in the brain: serotonin, dopamine, and glutamate. We summarize evidence from genetic, neuroimaging, animal model, and other lines of investigation that probe these three systems in patients with OCD. We also review recent work on predictors of response to current treatments. While many studies suggest abnormalities that may provide insight into the pathophysiology of the disorder, most studies have been small, and non-replication of reported findings has been common. Nevertheless, the gradual accrual of evidence for neurotransmitter dysregulation may in time lead the way to new pharmacological strategies.

Etiological factors and treatment challenges in an adolescent male with body dysmorphic disorder: A case report

There are very few existing reports in adolescents about the clinical presentation and treatment challenges associated with body dysmorphic disorder coexisting with suicidal behaviour. This case report describes a 13-year old male with body dysmorphic disorder, who was completely convinced that his belief related to the disorder is true (delusional belief) and therefore had no insight into his condition. His preoccupation with the shape of his nose progressed significantly over a 2-year period to the extent that he wore a surgical mask on a daily basis to camouflage the perceived defect. The distress due to the persistent preoccupation and intrusive thinking became so severe that he started to experience suicidal ideation and attempted suicide twice with no harm sustained. This case report focuses on three treatment challenges faced by the treating team: the need of continued treatment with pharmacotherapy and psychotherapy following a cosmetic procedure, the impact of the mother’s preoccupation with her physical appearance on the recovery of the young person, and the management of suicidality. We have also highlighted the probable causative factors of the development of the illness in this patient which are consistent with the established aetiology of body dysmorphic disorder.

Psychiatric Disorders in Facial Plastic Surgery

Body dysmorphic disorder and borderline personality disorder are common in esthetic practices and occur in up to 15% of patients. Operating on these patients may not only lead to dissatisfaction but may also worsen their premorbid condition and can induce negative behavior toward the practice. Preventing surgery and referring patients for cognitive therapy is essential. An adequate understanding of these conditions and the available screening tools is indispensable for all esthetic practitioners. Unrealistic emotional attribution to a facial shape, multiple procedures, a near-normal nose at the outset, childhood trauma, multiple comorbid mental conditions, and social dysfunction are red-flags to consider.

[Suicide risk in somatoform disorders]

BACKGROUND

The somatoform disorders include a group of complex disorders consist of somatic symptoms for which there are no identifiable organic cause or pathogenetic mechanisms. Given the importance of these disorders and the need to clarify the diagnosis of somatoform disorder affecting the suicide risk, we took into consideration the scientific literature to investigate the correlation between the two conditions.

METHODS

We performed a bibliographic search through Medline, Embase, PsycINFO, Scopus, SciELO, ORCID, Google Scholar, DOAJ using the following terms: somatoform, somatization disorder, pain disorder AND psychological factor, suicide, parasuicide, suicidality.

RESULTS

In all studies reported in our review, the suicidal behavior risk is high. But in the majority, the data are relatively unreliable because it takes into account the category nosographic "Neurotic, stress-related and somatoform disorders", too wide to be able to identify the clinical characteristics of patients at risk of only somatoform disorder.

CONCLUSIONS

Several studies conclude that psychiatric comorbidity increases the suicide risk: patients with two or more psychiatric disorders are more likely to commit a suicide attempt; in particular if there is a axis I diagnosis, the risk reduplicate. The somatization disorder seems to have a significant psychiatric comorbidity in particular with anxious and affective disorders spectrum.

OCD is associated with an altered association between sensorimotor gating and cortical and subcortical 5-HT1b receptor binding

Obsessive-compulsive disorder (OCD) is characterized by impaired sensorimotor gating, as measured using prepulse inhibition (PPI). This effect may be related to abnormalities in the serotonin (5-HT) system. 5-HT1B agonists can impair PPI, produce OCD-like behaviors in animals, and exacerbate OCD symptoms in humans. We measured 5-HT1B receptor availability using (11)C-P943 positron emission tomography (PET) in unmedicated, non-depressed OCD patients (n=12) and matched healthy controls (HC; n=12). Usable PPI data were obtained from 20 of these subjects (10 from each group). There were no significant main effects of OCD diagnosis on 5-HT1B receptor availability ((11)C-P943 BPND); however, the relationship between PPI and (11)C-P943 BPND differed dramatically and significantly between groups. 5-HT1B receptor availability in the basal ganglia and thalamus correlated positively with PPI in controls; these correlations were lost or even reversed in the OCD group. In cortical regions there were no significant correlations with PPI in controls, but widespread positive correlations in OCD patients. Positive correlations between 5-HT1B receptor availability and PPI were consistent across diagnostic groups only in two structures, the orbitofrontal cortex and the amygdala. Differential associations of 5-HT1B receptor availability with PPI in patients suggest functionally important alterations in the serotonergic regulation of cortical/subcortical balance in OCD.

Comorbidity between obsessive-compulsive disorder and body dysmorphic disorder: prevalence, explanatory theories, and clinical characterization

BACKGROUND

With the advent of the fifth edition of Diagnostic and Statistical Manual of Mental Disorders, body dysmorphic disorder (BDD) has been subsumed into the obsessive-compulsive disorders and related disorders (OCDRD) category.

OBJECTIVE

We aimed to determine the empirical evidence regarding the potential relationship between BDD and obsessive-compulsive disorder (OCD) based on the prevalence data, etiopathogenic pathways, and clinical characterization of patients with both disorders.

METHOD

A comprehensive search of databases (PubMed and PsycINFO) was performed. Published manuscripts between 1985 and May 2015 were identified. Overall, 53 studies fulfilled inclusion criteria.

RESULTS

Lifetime comorbidity rates of BDD-OCD are almost three times higher in samples with a primary diagnosis of BDD than those with primary OCD (27.5% vs 10.4%). However, other mental disorders, such as social phobia or major mood depression, are more likely among both types of psychiatric samples. Empirical evidence regarding the etiopathogenic pathways for BDD-OCD comorbidity is still inconclusive, whether concerning common shared features or one disorder as a risk factor for the other. Specifically, current findings concerning third variables show more divergences than similarities when comparing both disorders. Preliminary data on the clinical characterization of the patients with BDD and OCD indicate that the deleterious clinical impact of BDD in OCD patients is greater than vice versa.

CONCLUSION

Despite the recent inclusion of BDD within the OCDRD, data from comparative studies between BDD and OCD need further evidence for supporting this nosological approach. To better define this issue, comparative studies between BDD, OCD, and social phobia should be carried out.

Effectiveness of paroxetine in the treatment of obsessive–compulsive disorders

Clomipramine ushered in a new age of pharmacotherapy for obsessive-compulsive disorders, and it also facilitated our understanding of the biological aspects of obsessive-compulsive disorder, focusing on the serotonergic systems. The introduction of selective serotonin reuptake inhibitors has led to great progress in the pharmacological study of obsessive-compulsive disorder based on the serotonin hypothesis. Currently, selective serotonin reuptake inhibitors are positioned as a first-line drug of obsessive-compulsive disorder pharmacotherapy in the various guidelines and algorithms. Among six different selective serotonin reuptake inhibitors (paroxetine, sertraline, fluoxetine, fluvoxamine, citalopram, escitalopram) that are available worldwide, paroxetine has the broadest treatment spectrum and promises great benefits not only for obsessive-compulsive disorder patients, but also for those with comorbid depression and/or various kinds of anxiety disorders. This paper presents several clinical trials of paroxetine carried out, and discusses and reviews the therapeutic strategies for obsessive-compulsive disorder.

Body Dysmorphic Disorder: Neurobiological Features and an Updated Model

Body Dysmorphic Disorder (BDD) affects approximately 2% of the population and involves misperceived defects of appearance along with obsessive preoccupation and compulsive behaviors. There is evidence of neurobiological abnormalities associated with symptoms in BDD, although research to date is still limited. This review covers the latest neuropsychological, genetic, neurochemical, psychophysical, and neuroimaging studies and synthesizes these findings into an updated (yet still preliminary) neurobiological model of the pathophysiology of BDD. We propose a model in which visual perceptual abnormalities, along with frontostriatal and limbic system dysfunction, may combine to contribute to the symptoms of impaired insight and obsessive thoughts and compulsive behaviors expressed in BDD. Further research is necessary to gain a greater understanding of the etiological formation of BDD symptoms and their evolution over time.

A link between oxytocin and serotonin in humans: supporting evidence from peripheral markers

Pharmacological studies indicate a functional interaction between the serotonergic and oxytocinergic systems. In particular, some selective serotonin (5-HT) reuptake inhibitors, such as citalopram and fluvoxamine, seem to exert part of their antidepressant effects through oxytocin (OT) release. Further, the administration of fenfluramine, a serotonergic agonist, to healthy subjects increases plasma OT levels. Interestingly, immunocytochemical and double-immunofluorescent techniques revealed a high degree of overlap between 5-HT transporter (SERT)-labeled fibers and OT-containing cells in the paraventricular and supraoptic nuclei of primate hypothalamus. These findings suggest that the influence of 5-HT on OT system might be mediated by SERT. In this study, we explored the possible existence of a link between OT and SERT in human subjects, by means of two peripheral markers, the platelet SERT, as measured by [³H]-paroxetine ([³H]-Par) binding, and plasma OT levels. As far as [³H]-Par binding parameters are concerned, the Bmax (mean ± SD, fmol/mg protein) was 1155 + 130 and the Kd (mean ± SD, nM) was 1.31 ± 0.61. The OT plasma levels (mean ± SD, pg/ml) were 1.14 ± 1.07. A significant and positive correlation was found between plasma OT levels and Kd values (correlation coefficient: r: 0.466, p = .038). This result represents the first evidence of an interaction between OT and SERT, as measured by [³H]-Par binding, at peripheral levels in humans. Given the several activities mediated by both OT and 5-HT, such a relationship might provide new perspectives and insights into psychiatric disorders and/or social relationship disturbances, as well as novel treatment strategies overcoming and/or integrating the serotonergic paradigm.

[An old "new" disease: body dysmorphic disorder (dysmorphophobia)]

Body dysmorphic disorder causes significant suffering and serious impairment in psychosocial functions. However, this disease with dangerous risks is scarcely mentioned in the Hungarian medical literature. The objective of the author is to give a detailed review about this almost unknown, but relatively common disorder. The serious disorder of body perception is in the centre of symptoms, leading to social isolation, anxiety, depression and obsessive-compulsive phenomena. The disorder often remains unrecognized because of the lack of insight of disease. Comorbidity with affective disorders, anxiety disorders, personality disorders, eating disorders, alcoholism and substance use disorders is common. The life quality of affected patients is bad, the risk of suicide or violence is high. Biological, psychological and sociocultural factors play an important role in the etiopathogenesis of the disorder. Imaging techniques and neuropsychological measures revealed changes characteristic for the disease. Childhood abuse and neglect, appearance-related critical remarks, stressors and the impact of media are also supposed to have role in the development of the disorder. The point prevalence is 0.7-2.5% in the general population, however, in special groups such as in tertiary students, psychiatric, dermatological and cosmetic surgery patients the prevalence rates may be much higher. Typically, the disease begins in early adolescence, and it persists and deteriorates without treatment, showing a chronic course. By means of pharmacotherapy and/or psychotherapy long-during improvement or full recovery can be achieved within a relatively short period of time.

Should an obsessive-compulsive spectrum grouping of disorders be included in DSM-V?

The obsessive-compulsive (OC) spectrum has been discussed in the literature for two decades. Proponents of this concept propose that certain disorders characterized by repetitive thoughts and/or behaviors are related to obsessive-compulsive disorder (OCD), and suggest that such disorders be grouped together in the same category (i.e. grouping, or "chapter") in DSM. This article addresses this topic and presents options and preliminary recommendations to be considered for DSM-V. The article builds upon and extends prior reviews of this topic that were prepared for and discussed at a DSM-V Research Planning Conference on Obsessive-Compulsive Spectrum Disorders held in 2006. Our preliminary recommendation is that an OC-spectrum grouping of disorders be included in DSM-V. Furthermore, we preliminarily recommend that consideration be given to including this group of disorders within a larger supraordinate category of "Anxiety and Obsessive-Compulsive Spectrum Disorders." These preliminary recommendations must be evaluated in light of recommendations for, and constraints upon, the overall structure of DSM-V.

Human serotonin transporter expression during megakaryocytic differentiation of MEG-01 cells

The serotonin (5-HT) transporter (SERT) has been found altered in platelets of patients with genetically complex disorders, including mood-anxiety, pain and eating disorders. In this study, we used cell cultures of platelet precursors as models of investigation on mechanisms of SERT regulation: SERT expression was appraised during megakaryocytic differentiation of human megakaryoblastic MEG-01 cells. Cells were cultured for 8 days with 10(-7)M 4-beta-12-tetradecanoylphorbol-13-acetate (beta-TPA) in the presence of 10% fetal bovine serum (FBS) and SERT was assessed by real time PCR, immunofluorescence microscopy, Western blot and [(3)H]5-HT re-uptake. Results revealed that SERT is present in control-untreated MEG-01 cells. beta-TPA-differentiating MEG-01 cells showed a redistribution of SERT fluorescence, diffuse to cell bodies and blebs along with a 3-fold SERT mRNA increase and a moderate raise in SERT protein (1.5/1.4-fold) by immunoblot and re-uptake assays. In summary, we have shown herein that control megakaryoblasts express the SERT protein. SERT is modulated by differentiation events, implying that SERT density in platelets is under the control of megakaryocytopoiesis stages. Differentiation of MEG-01 cells can provide considerable insight into interactions between SERT genetics, transmitter-hormonal/homeostatic mechanisms and signaling pathways.

Association of the serotonin transporter polymorphism and obsessive-compulsive disorder: systematic review

We investigated the association between the long (l) and short (s) alleles of the serotonin transporter polymorphism (5-HTTLPR) in the promoter region of the SLC6A4 gene and obsessive-compulsive disorder (OCD) using meta-analysis to combine all published data from case-control and family based association studies (2,283 cases). In stratified meta-analysis we investigated whether age of sample (child and adult), ethnicity (Caucasian and Asian) and study design (case-control and family-based association studies) moderated any association. In the overall meta-analysis we found no evidence of association between genetic variation at the 5-HTTLPR locus and OCD. We did find significant heterogeneity between studies. In the stratified meta-analyses, we demonstrated a significant association between the l-allele and OCD in family-based association studies and in studies involving children and Caucasians. Our meta-analysis suggests the possibility that the l-allele may be associated with OCD in specific OCD subgroups such as childhood-onset OCD and in Caucasians. Further meta-analyses based on individual patient data would be helpful in determining whether age of OCD onset, gender and the presence of comorbid illness (e.g., tics) moderates the relationship between 5-HTTLPR and OCD.

ATP, calcium and magnesium levels in platelets of patients with primary fibromyalgia

OBJECTIVES

To evaluate the intracellular levels of the high energy adenosine triphosphate nucleotide ATP and essential divalent cations, calcium and magnesium, in platelets of patients affected by primary fibromyalgia syndrome (FMs).

DESIGN AND METHOD

Platelet ATP and cation concentrations were measured in 25 patients affected by FMs and 25 healthy volunteers through a chemiluminescent and a fluorimetric assay, respectively.

RESULTS

Significant lower ATP levels were observed inside platelets of FM patients (fmol ATP/plt: 0.0169+/-0.0012 vs. healthy controls, fmol ATP/plt: 0.0306+/-0.0023, mean+/-SEM) (*** P<0.0001). A trend towards higher calcium concentrations (P=0.06) together with significant increased magnesium levels were also reported in platelets of patients by comparison with controls (P=0.02).

CONCLUSIONS

This preliminary study suggests that disturbances in the homeostasis of platelet ATP metabolism-signaling and calcium-magnesium flows might have a relevance in the pathogenesis of FMs.

The pathophysiology of body dysmorphic disorder

Body dysmorphic disorder (BDD) is an often severe and disabling condition, affecting up to 2% of the population. Despite its prevalence and clinical significance, very little is known about the pathophysiology of BDD. However, clues to its possible neurobiological substrates and abnormalities in information processing are starting to emerge. This article reviews findings from genetic, brain lesion, neuroimaging, neuropsychological, and psychopharmacological studies that have allowed us to develop a tentative model of the functional neuroanatomy of BDD. There is likely a complex interplay of dysfunctions in several brain networks underlying the pathophysiology of BDD. A combination of dysfunctions in frontal-subcortical circuits, temporal, parietal, and limbic structures, and possibly involving hemispheric imbalances in information processing, may produce both the characteristic symptoms and neurocognitive deficits seen in BDD. An improved understanding of the pathophysiology of BDD will be crucial to guide the development of better treatments.

Alteration of serotonin transporter density and activity in fibromyalgia

The aim of the study was to evaluate the kinetic parameters of a specific serotonin transporter (SERT) and serotonin uptake in a mentally healthy subset of patients with fibromyalgia. Platelets were obtained from 40 patients and 38 healthy controls. SERT expression and functionality were evaluated through the measurement of [³H]paroxetine binding and the [³H]serotonin uptake itself. The values of maximal membrane binding capacity (B_max) were statistically lower in the patients than in the healthy volunteers, whereas the dissociation constant (K_d) did not show any statistically significant variations. Moreover, a decrease in the maximal uptake rate of SERT (V_max) was demonstrated in the platelets of patients, whereas the Michaelis constant (K_m) did not show any statistically significant variations. Symptom severity score (tiredness, tender points index and Fibromyalgia Impact Questionnaire) were negatively correlated with B_max and with V_max, and positively correlated with K_m. A change in SERT seems to occur in fibromyalgic patients, and it seems to be related to the severity of fibromyalgic symptoms.

Kleptomania: comorbid psychiatric diagnosis in patients and their families

OBJECTIVES

Kleptomania, defined by DSM-IV as the inability to resist the impulse to steal objects which are not needed for personal use or for their monetary value, may reflect a form of obsessive-compulsive spectrum disorder and/or affective spectrum disorder.

METHODS

Twenty-one kleptomanic patients and 57 first-degree relatives completed a semistructured DSM-IV-based interview and questionnaires. Questionnaires are: the HDRS-17 (the Hamilton Rating Scale for Depression), the HARS (Hamilton Rating Scale for Anxiety), the Y-BOCS (Yale-Brown Obsessive Compulsive Scale), the YMRS (Young Mania Rating Scale). The two groups were compared to demographically matched normal controls (n = 64).

RESULTS

We found a high prevalence of affective and anxiety disorders in our sample of kleptomanic patients and their first-degree relatives. In addition, the scores on the HDRS, HARS, and Y-BOCS were significantly higher in the study group than in the control group.

CONCLUSIONS

Our finding of a high prevalence of psychiatric comorbidity in kleptomanic patients could lead to the development of new treatment strategies for this disorder. Furthermore, the pattern of psychiatric disorders seen in the first-degree relatives can lead to new insights about the nosology and etiopathology of kleptomania.

Kleptomania in impulse control disorders, obsessive-compulsive disorder, and bipolar spectrum disorder: clinical and therapeutic implications

This paper aims to critically review currently available data on kleptomania and to analyze the possible future evolution of clinical research and therapeutic strategies.

The obsessive-compulsive spectrums

Because of the paucity of research on the OCSDs, it seems premature to cluster these putative disorders together in DSM, to combine delusional and nondelusional variants of OCSDs, or to classify OCSDs dimensionally. Further investigation of the OC spectrums is clearly needed. These constructs are powerful and useful heuristics with potential validity and clinical utility. The putative OC spectrum and its subspectrums have some apparent advantages over current conceptualizations of these disorders. They may prove more consistent with empirical evidence and ultimately may be shown to better reflect these disorders' pathogenesis. Importantly, they also may be more useful and valid guides for clinical practice.

Cerebrospinal fluid interleukin-6 in obsessive-compulsive disorder and trichotillomania

Recent studies have suggested that neuroimmune abnormalities may play an important role in the pathogenesis of obsessive-compulsive disorder (OCD) and related disorders. This study was undertaken to determine whether cerebrospinal fluid (CSF) concentrations of the proinflammatory cytokine interleukin (IL)-6 differ between OCD and trichotillomania patients and healthy control subjects. Lumbar puncture with a standardized procedure was performed on 26 patients with OCD and 9 with trichotillomania. All patients were drug-free and met DSM-IV criteria. Twenty-six age- and sex-matched healthy volunteers underwent the same procedure. CSF was assayed for IL-6 using a quantitative 'sandwich' enzyme immunoassay technique. Mean+/-S.D. CSF IL-6 levels did not differ between OCD patients (n=26) (2.4+/-1.1 pg/ml) and controls (n=26) (2.4+/-1.9 pg/ml) or between trichotillomania patients (n=9) (2.3+/-0.8 pg/ml) and their matched controls (n=14) (1.9+/-0.5 pg/ml). These findings fail to support speculation that ongoing immune activation may be causally involved in the pathogenesis of OCD or trichotillomania.

Polymorphism of the serotonin transporter: implications for the use of selective serotonin reuptake inhibitors

Selective serotonin reuptake inhibitors (SSRIs) are used to treat a number of psychiatric disorders related to mood and anxiety, and variations in the serotonin transporter (5-HTT) gene may be involved in a number of these. A polymorphic site in the promoter region is associated with differences in 5-HTT gene expression. Studies suggest that the short allele of the 5-HTT promoter (5-HTTPR) site can adversely influence the antidepressant response to SSRIs, and is associated with anxiety-related traits, depression, and impulsive disorders such as alcohol abuse. Several studies do not replicate these findings; potential confounding factors include age, gender, and population stratification. Other 5-HTT polymorphisms also exist. For example, individuals with the short allele of a variable number of tandem repeats (VNTR) polymorphism, located in the second intron, may have reduced responsiveness to SSRIs, and the STin2.12 allele at this site has been associated with bipolar disorder. Findings both supporting and inconsistent with these conclusions are reviewed. The clinical effects of the polymorphisms may be associated with effects on platelets, neural 5-HTT levels, and indices of serotonergic function.

Kleptomania: diagnosis and treatment options

Kleptomania--the inability to resist the impulse to steal objects, not for personal use or monetary gain--is currently classified in psychiatric nomenclature as an impulse control disorder. However, some of the principle features of the disorder, which include repetitive intrusion thoughts, inability to resist the compulsion to perform the thievery and the relief of tension following the act, suggest that kleptomania may constitute an obsessive-compulsive spectrum disorder. Kleptomania is commonly under-diagnosed and is often accompanied by other psychiatric conditions, most notably affective, anxiety and eating disorders, and alcohol and substance abuse. Individuals with the disorder are usually referred for treatment due to the comorbid psychiatric complaints rather than kleptomanic behaviour per se. Over the past century there has been a shift from psychotherapeutic to psychopharmacological interventions for kleptomania. Pharmacological management using selective serotonin (5-hydroxytryptamine; 5-HT) reuptake inhibitors (SSRIs) and other antidepressants, mood stabilisers and opioid receptor antagonists, as adjuvants to cognitive-behavioural therapy, has produced promising results.

Psychopathology and personality characteristics in relation to blood serotonin in Tourette's syndrome and obsessive-compulsive disorder

Family studies suggest an interrelationship between Gilles de la Tourette Syndrome (GTS) and some forms of obsessive-compulsive disorder (OCD). Some authors consider GTS to be part of a serotonergically mediated cluster of OCD spectrum disorders. The present study was undertaken to compare measures of psychopathology, personality and blood serotonin between GTS and OCD (without tics), and to investigate whether an OCD spectrum hypothesis is supported for GTS. Fifteen GTS without OCD subjects, 21 tic with (+) OCD subjects, 15 OCD without tic subjects and 26 controls (all without serotonergic medication) were evaluated with self-rated and clinician-rated measures of psychopathology and personality. Whole blood serotonin (5-HT) and platelet monoamine oxidase activity (MAO) was measured, and Spearman's correlations were calculated between whole blood 5-HT, MAO and rating scale scores within the entire sample and within subgroups. There were main effects of OCD on anxiety, obsessive-compulsive, neuroticism and extraversion scores. There were main effects of tics on depression, obsessive-compulsive, trait anxiety and neuroticism scores, and on platelet MAO. There were interaction effects on platelet MAO, 5-HT, Yale-Brown Obsessive-Compulsive Rating Scale severity, trait anxiety and Eysenck Personality Questionnaire neuroticism scores. Platelet MAO activity was elevated in tic-free OCD subjects when compared to tic + OCD, GTS without OCD and controls. Whole blood 5-HT was lowered in tic + OCD patients in comparison to GTS without OCD and tic-free OCD subjects. Whole blood 5-HT and obsessive-compulsive severity were negatively correlated within OCD without tic patients and MAO and Leyton Obsessive Inventory scores were negatively related within GTS without OCD patients. The biochemical data of this study suggest that in tic + OCD and in tic-free OCD patients, 5-HT dysregulations play a role, but not necessarily in pure GTS. Serotonergic dysregulations within tic + OCD and tic-free OCD patients are distinct, suggesting differences in underlying pathophysiology. The finding that obsessions and compulsions can be associated with either 5-HT hypofunctionality or hyperfunctionality reveals a major weakness in the OCD spectrum theory, i.e. that the associations between obsessive-compulsive behaviours and 5-HT abnormalities are less specific than suggested by the original obsessive-compulsive spectrum model.