The Spectrum Approach in Psychopathology: Neurosis, Psychosis, and Neurodiversity

The historical transformation of neurosis and psychosis, neurodevelopmental intersections between autism and ADHD (AuDHD), and the autism-schizophrenia link (PAUSS, ZAQ).

From Classic Dichotomy to Modern Classification: The Conceptual Transformation of Neurosis and Psychosis

For many years, the history of clinical psychiatry and psychology was shaped around the dichotomy of neurosis and psychosis, which is based on an individual's relationship with reality. In traditional diagnostic approaches, neurosis was used to define milder mental disorders where the individual did not lose their perception of reality or reality testing and was aware of their symptoms like anxiety, obsessions, phobias, or depression (preserved insight).

Neurotic disorders, while not completely destroying an individual's daily functioning, are closely associated with psychological stress factors that severely reduce quality of life. The concept of neurosis is divided into specific subtypes:

Phobic Neurosis: The individual displays exaggerated and unrealistic anxiety reactions even when no concrete danger or stressor is present.

Generalized Anxiety Neurosis: Characterized by a vague, pervasive sense of dread and fear.

Depressive Neurosis: A general depressive state marked by the inability to enjoy daily activities, grief, reluctance, sluggishness, and finding life completely meaningless.

Hysterical Neurosis (Somatic Conversion): Manifests through somatic symptoms such as acting paralyzed or being unable to move a limb even though no physiological or organic disorder is detected.

Obsesive Neurosis: Characterized by uncontrollable, repetitive, and disturbing obsessions (e.g., involuntary thoughts of jumping from a high place or smothering one's baby).

Psychosis, on the other hand, is a clinical condition where a person's connection with reality is broken, and their thought, emotional, and behavioral processes are severely affected. Psychotic individuals experience hallucinations (sensory perceptions like hearing voices or seeing things in the absence of external stimuli) and delusions (irrational beliefs that remain unshaken despite contrary evidence). Psychosis, associated with severe mental illnesses such as schizophrenia, bipolar disorder, or schizoaffective disorder, can stem from neurotransmitter imbalances, genetic predispositions, and traumatic experiences, and often requires hospitalization.

Historically, a clinical group situated exactly on the border of the psychotic and neurotic spectra has been defined, characterized by a lack of integrated identity but preserved reality testing, using primitive defense mechanisms. Termed Borderline Personality Organization (BPO), this structure is distinguished from neuroses by identity diffusion and from psychoses by the absence of delusions and hallucinations.

The definition of neurosis, which held an important place in traditional classifications, was completely removed from official international psychiatric manuals starting with DSM-III-R (1987) and ICD-10 (1992), replaced by more specific and measurable categories of anxiety, somatoform, and obsessive-compulsive disorders.

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The Neurodevelopmental Spectrum: The Relationship Between Autism Spectrum Disorder and ADHD

In the ICD-11 classification published by the World Health Organization, neurodevelopmental disorders are defined as conditions starting in early childhood, characterized by deviations in brain development, and following a lifelong course. Autism Spectrum Disorder (ASD) and Attention Deficit Hyperactivity Disorder (ADHD) are the most common neurodevelopmental conditions encountered in clinical practice.

While simultaneous diagnosis of these two disorders was not permitted in past manuals, co-occurring (comorbid) diagnosis has gained official status with DSM-5 and ICD-11. Current literature shows that 15% to 25% of children and adolescents diagnosed with ADHD also meet ASD diagnostic criteria, while a very high rate of 50% to 70% of individuals with ASD have an accompanying ADHD presentation. This comorbidity is clinically referred to as the AuDHD phenotype.


Disorder Code (ICD-11)	ICD-11 Classification Title	ICD-10 Equivalent	DSM-5 Equivalent	Clinical Focus
6A00	Disorders of Intellectual Development	F70–F79 (Mental Retardation)	Intellectual Disability	General limitations in cognitive and adaptive functions.
6A01	Developmental Speech or Language Disorders	F80, F98.5, F98.6	Communication Disorders	Deficits in verbal expression, articulation, and pragmatic language.
6A02	Autism Spectrum Disorder	F84 (Pervasive Developmental Disorder)	Autism Spectrum Disorder	Social interaction deficits, restricted/repetitive interests, and insistence on routine.
6A02.0	ASD without disorder of intellectual development and with mild or no impairment of functional language	F84.5 (Asperger Syndrome)	ASD (without accompanying intellectual/language impairment)	Social-pragmatic difficulties accompanying normal cognitive levels and fluent language.
6A02.1	ASD with disorder of intellectual development and with mild or no impairment of functional language	F84.0 (Childhood Autism)	ASD (with accompanying intellectual impairment)	Lower cognitive performance level but preserved verbal communication skills.
6A02.3	ASD with disorder of intellectual development and with impaired functional language	F84.0 (Atypical/Childhood Autism)	ASD (with accompanying intellectual and language impairment)	Severe cognitive delay and restricted verbal communication skills.
6A03	Developmental Learning Disorder	F81 (Disorders of Scholastic Skills)	Specific Learning Disorder	Developmental limitations in reading, writing, or mathematics.
6A04	Developmental Motor Coordination Disorder	F82 (Motor Function Disorder)	Motor Disorders	Age-inappropriate clumsiness and incoordination in fine and gross motor skills.
6A05	Attention Deficit Hyperactivity Disorder	F90 (Hyperkinetic Disorders)	Attention-Deficit/Hyperactivity Disorder	Persistent symptoms of inattention, hyperactivity, and impulsivity.
6A06	Stereotyped Movement Disorder	F98.4	Stereotypic Movement Disorder	Non-functional, repetitive rhythmic motor behaviors.
8A05.0	Primary Tics or Tic Disorders	F95	Tourette's Disorder / Persistent Tics	Involuntary, sudden, and repetitive motor or vocal movements.

The "AuDHD" clinical phenotype, where ASD and ADHD are observed together, has a compounding (*additive*) disruptive effect on the individual's academic, occupational, and social functioning. The primary clinical distinctions between these two conditions are shaped around attention spans, communication patterns, and adherence to routines: 1. Attention and Focus: Individuals with ADHD struggle to sustain attention on a single focus, are easily distracted by external stimuli, and experience problems with impulsivity and self-regulation. Autistic individuals, however, have much narrower interests; they can sustain extraordinary focus (hyperfocus) on topics they enjoy or develop special interests in, while remaining entirely indifferent to subjects that do not interest them. 2. Communication Pattern: A person with ADHD displays impulsivity-based behaviors such as talking excessively, interrupting others, avoiding eye contact due to impatience, and abandoning games midway. An autistic individual is characterized by deficits in Theory of Mind, such as an inability to use non-verbal communication tools (gestures, expressions), structural difficulties in initiating and sustaining social interactions, and challenges in developing empathy. 3. Approach to Routine: While individuals with ADHD quickly get bored with monotony and constantly seek variety and stimulation, autistic individuals insist heavily on sameness in their environment and can display intense anger or anxiety reactions in response to the slightest deviation in their daily routines. The combination of these two conditions drags the individual into an intense internal conflict (AuDHD Paradox), where they seek novelty while being unable to abandon routines.

Furthermore, this comorbidity increases the frequency of sleep disorders; while sleep problems due to ADHD are between 50% and 74% in children and adolescents, this rate rises up to 80% in autistic individuals.

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The Intersection of Autism and Schizophrenia: Historical Process, Biological Connections, and Clinical Overlaps

The autism and schizophrenia spectra are two entities that have long been intertwined in the history of clinical psychiatry. When Swiss psychiatrist Paul Eugen Bleuler first used the term "autism" in 1911, he defined it as a core symptom describing schizophrenia patients withdrawing into their inner worlds by detaching from external reality. Until the mid-20th century, autistic children were often monitored under the diagnosis of "childhood-onset schizophrenia" (COS).

Russian child psychiatrist Grunia Sukhareva, in her studies as early as 1924, described a group of children carrying autistic traits (later popularized by Leo Kanner and Hans Asperger) and noticed that these children, unlike schizophrenia patients, did not show cognitive regression (deterioration) over time, but rather continued their development. Sukhareva's paper published in 1925, which emphasized flat affect, stereotypic speech, restricted interests, and hypersensitivity to specific sounds and smells, is almost a direct historical precursor to modern DSM-5 autism criteria. Studies conducted by Israel Kolvin in the early 1970s clearly separated "early-onset psychosis" (autism), which presents with compulsive and ritualistic behaviors, from "late-onset psychosis" (schizophrenia), characterized by thought disorders and hallucinations, reflecting this distinction in the DSM-III manual in 1980.

Modern genetic and neurobiological research provides strong evidence for the shared origins of these two conditions:

Genetic Overlap: While the heritability of schizophrenia is around 80%, the risk genes and chromosomal variations involved in the etiology of both disorders overlap by approximately 15% to 25%.

Neuroimaging: Neuroimaging studies show that individuals with both ASD and schizophrenia have lower gray matter volume in limbi-striato-thalamic neural networks. However, this volume decrease is concentrated in the amygdala, caudate nucleus, frontal and medial gyri in schizophrenia, and specifically in the putamen in autism.

E/I Balance: An imbalance between excitatory (glutamatergic) and inhibitory (GABAerjik) synaptic transmission in cortical activity (E/I imbalance) is thought to play a role in the pathophysiology of both conditions.

In clinical practice, the negative symptoms of these two conditions overlap intensely. Negative symptoms observed in schizophrenia, such as flat or blunt affect (inability to express emotions, restricted gestures/expressions), alogia (poverty of speech content and fluency), avolition (apathy, inability to initiate action), and anhedonia (inability to feel pleasure), can easily be confused with autism's restricted social-emotional reciprocity, monotonic speech tone, social withdrawal, and restricted non-verbal communication. There is a direct link between disorganized or impoverished speech patterns in schizophrenia and pragmatic language deficits in autism. Autistic individuals' stereotypic motor movements and restricted interests can parallel catatonic behaviors and delusions in schizophrenia. Furthermore, both groups face serious psychosocial risks, such as high rates of self-harm (up to 50% in schizophrenia), suicidal ideation, and substance abuse.

In the differential diagnosis process, focusing on "positive" symptoms is of vital importance:

Positive symptoms distinguishing the schizophrenia group are true delusions and hallucinations, while restricted/repetitive behaviors and stereotypic language use are prominent in autism.

However, it is known that 47% of autistic individuals report abnormal perceptual experiences, such as objects changing shape, and 63% report sub-clinical "psychotic-like symptoms" such as feeling touched when alone. Yet, these perceptual differences must be distinguished from the complete loss of reality and delusions in schizophrenia.

Delusional thoughts observed in autistic individuals are often expansive, referential, or persecutory, and typically develop as a result of peer bullying or social isolation.

Examining other conditions in the differential diagnosis: Rett Syndrome begins with a distinct regression in social interaction between 1–4 years of age but is distinguished from autism by subsequent improvements in social communication skills. In Selective Mutism, early child development is normal, and reciprocal social interaction capacity is fully preserved in safe environments like the home. Social Pragmatic Communication Disorder is distinguished from ASD by the complete absence of repetitive and restricted behavioral patterns historically or currently.

In clinical measurement and evaluation, the PANSS Autism Severity Score (PAUSS) is an important transdiagnostical tool developed to quickly and reliably detect autistic symptoms within the schizophrenia spectrum. PAUSS consists of 8 specific items from the standard PANSS scale: N1 (blunt affect), N3 (poor rapport), N4 (passive/apathetic social withdrawal), N5 (difficulty in abstract thinking), and N6 (lack of spontaneity and flow of conversation). The internal consistency of the scale is extremely high (Cronbach's $\alpha = 0.869$), showing strong convergent validity with the gold-standard ADOS and ADI-R clinical interviews (PAUSS AuC value is $0.824$, while ADOS AuC is $0.916$).

Research confirms that "autistic schizophrenia" patients with a PAUSS score over 30 display much worse neurocognitive performance in WAIS-R subtests (digit span, vocabulary, arithmetic, similarities) and experience significant functional losses in the Facial Emotion Identification Test (FEIT) and general social cognition tests (the SCOPE study). Additionally, newer scales like the 134-item SchiZotypy Autism Questionnaire (ZAQ), developed to distinguish the gray zone between autism and schizotypal disorders, improve differential diagnosis accuracy.

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Childhood ADHD Symptoms and Adult Psychosis Risk

Epidemiological and longitudinal follow-up studies reveal that individuals diagnosed with ADHD in childhood and adolescence carry a 4.3 to 4.59 times higher risk of developing schizophrenia spectrum disorders in adulthood compared to neurotypical controls. This remarkable statistic highlights shared neurodevelopmental origins and transdiagnostical risk factors.

There is a significant symptomatic overlap between ADHD symptoms and clinical states carrying an ultra-high risk (UHR) for psychosis:

Executive Function Deficits: Impairments in working memory, sustained attention, processing speed, and cognitive flexibility form both the core structure of ADHD and are considered the strongest cognitive markers emerging during the prodromal (pre-symptom) period of schizophrenia.

Emotional Regulation Deficits: Low frustration tolerance, emotional lability, internal tension, and anxiety reactions to stressors are heavily observed in both groups.

Disorganized Behavior Patterns: Disorganized thought processes and behavioral disorganization parallel impulsive-motor excesses in ADHD and behavioral coordination losses in the early stages of schizophrenia.

Another important dimension in terms of clinical management is the use of dopaminergic stimulant medications widely used in ADHD treatment. In children and youth who are genetically predisposed to schizophrenia or are already in the prodromal phase, the use of these medications increases dopamine levels and can, albeit rarely, trigger acute psychotic breaks.