Symptoms of Schizophrenia: the dopamine theory


Schizophrenia is a mental condition with abnormal reality. Symptoms of schizophrenia are classified as negative, positive, cognitive, and mood symptoms.
Psychosis better explains the positive symptoms of schizophrenia. It is a condition where you lose touch with reality. Psychosis is a pure experience of restlessness and anxiety. A few parts are spiritual and beautiful, whereas others are haunting and terrifying. It also takes you on the path of your darkest depression. 

It is a myth to consider that psychotics are violent– they are in constant fear and act in anxiety. Psychosis is not persistent– It takes years of medications and therapies to attain continued stability. 

Though the primary reason for psychosis is a mental illness, it may not be the only reason. Trauma or abuse during childhood is also a reason. However, most of them cope up with the situation over time; only a few are affected and traumatized for life. They find it really difficult to cope with the trauma. They start to consider the problem in their lives as an aspect of personality and grow along with it. It does not necessarily mean they have a split personality.

Hallucinations and delusions– the primary symptoms of schizophrenia

Hallucinations are sensory experiences without any external stimulus. They fail to differentiate external and internal stimuli. The trigger always comes from the inside. The auditory hallucinations include voices, which are usually very frightening and threatening. They may also talk about self-harm and suicide. 

The voices sometimes constantly argue, get painfully louder, meaner, and persuasive over time. It induces confusion, and gradually takes control of the person. People also reported that the voice makes them feel insecure and always barges into their personal life. The voice makes the victims work for them. The visual hallucinations are more like looking and talking to a person who is not real. 

Delusions are beliefs against reality, i.e., false beliefs. In delusions, thoughts are often contrary to facts. They may constantly fear about someone following them or trying to kill them or their spouse cheating on them. Such experiences can make one paranoid and life-changing. They may even try to hurt themselves. 

In these situations of haunting hallucinations and horrifying delusions, it is important to empathise and comply, rather than denying their beliefs. At the same time make sure you don’t tell them that their delusions are real.

The underlying reason for psychotic symptoms of schizophrenia

When we talk about the neurobiology behind the psychotic symptoms, it is essential to note that there are multiple sources and multiple pathways. Since neurotransmitters are involved in the communication between the neural cells, they also play a crucial role in the expression of psychotic symptoms. Hence, one of the pathways and sources suggest hyperdopaminergia as a theory.

Hyperdopaminergia is a condition with excess dopamine in the system. High amounts of dopamine also serve as a diagnosis for mental health conditions like Alzheimer’s and Schizophrenia. Contrastingly, low dopamine suggests Parkinson’s disease.

The dopamine theory of psychosis

We know that substance and alcohol abuse can release dopamine into the system via the ventral tegmental area and the nucleus accumbens. The high content eventually settles near the cluster of cells. Substance abusers also reported cases of hallucinations and delusions– Drug-induced psychosis. It suggests the dopamine level as one of the underlying reasons for mania.

Dopamine functions in the limbic striatum have a direct impact on hippocampal control.

Doctors studied the brain of mentally-ill patients to discover high subcortical synaptic dopamine content and high basal dopamine synthesis. High L-dopa uptake is evident. These effects are observed in the associated striatum– Limbic striatum. It is the primary force behind the positive symptoms– hallucinations and delusions. However, presynaptic dopaminergic abnormalities are present before onset.

Moreover, individuals who enter the state of psychosis from mental illnesses express elevated levels comparatively. Consequently, dopamine depletion translates to a reduction in the positive symptoms, opening a route of treatment.

Excess dopamine in the system due to drug abuse may result in the psychotic symptoms but will not conclude schizophrenia as a diagnosis.

Regions of the brain involved in psychotic symptoms

  • The central circuit for hallucinatory experience involves the associated striatum, prefrontal cortex, and thalamus. The auxiliary circuits contribute to the effect.
  • Hypothalamus and thalamus are responsible for the auditory hallucinations. This condition loosely translates to alterations in thalamocortical connectivity. It also involves disruptions in temporal, hippocampal, and amygdala regions of the brain. However, occipital lobe, striatum, and thalamus play a role in the visual experience.
  • Overactivation of PFC results in delusions. It is also a consequence of diminished deactivation of thalamic networks.
  • Along with dysfunctions, brain lesions and injury also play a role in inducing hallucinations. Lesions interfere with the brain pathways associated with the stimulus– for instance, caudate lesions can express positive symptoms in one.

They lose touch with reality.

In the events of lesions and dopamine alterations, the person gradually loses insight and fails to differentiate reality from fantasy. Loss of insight also suggests disruptions in the corticostriatal networks. Moreover, loss of insight and delusionary belief is evident for the overactivation of PFC. PFC is an input to the limbic striatum, and any disruption can lead to a psychotic episode.

The false perceptions

On the other hand, thalamus relays information processing into the cortex. Thalamus circuits with the striatum and PFC and any disturbance impairs functionality. Low thalamic volume interferes with the processing mechanisms, resulting in false perceptions. Medication-naive patients, like the ultra risk patients, exhibit low thalamic and caudate volumes and are prone to frequent psychotic episodes. Thalamus connections also play a role in sensory and emotional effects

Conclusively, thalamus expresses its activity in the PFC exhibiting positive psychotic symptoms. Alternatively, amygdala and hippocampus feed into the circuit expressing its effect on thalamus– contributing to sensory hallucinations.

Negative symptoms of schizophrenia

Negative symptoms usually represent “loss”  of essential functions– forget to bath for days, or forget how to button-up a shirt. They have troubling focusing and concentrating– cognitive deficits in schizophrenia. Social isolation and withdrawal and lack of motivation are among the negative symptoms of schizophrenia. They can seem jumpy at times and sedentary some other time. 

Moreover, they can’t seem to enjoy anything anymore. Schizophreniacs express a lack of empathy and anxiety. They also have trouble following time.



Disorganized speech and thoughts

Disorganized speech and thought is a consequence of mental illnesses. If it is persistent without any medical condition, psychosis and schizophrenia is a better diagnosis. This condition is due to a decrease in grey matter volume over time. They mingle up words and sometimes talk so fast that it is difficult to comprehend (pressured speech).

While talking, they forget what they are actually speaking about and jump to a whole new topic (thought blocking). “Word salad” better describes the condition. They sometimes invent new words of their own (neologisms) and repeat words and sentences (perseverations).

How do antipsychotic medications work?

The basal ganglia play an essential role in the cortical inputs, maintaining the motor functioning.

Excess dopamine in the system disrupts the cortical pathway, exhibiting the positive symptoms.

Hence, antipsychotics target the D2 signaling– Dopamine antagonists. This process helps maintain the balance between D1 and D2 pathways. It is a responsive treatment of antipsychotics. 

In the D1 pathway, the D1 receptors convey the information directly to the basal ganglia, whereas the D2 route is indirect.

However, in psychotic medication, it is essential to note that all patients do not respond in the same way. There is a refractory response on the alternate pathway. In refractory response, we observe impaired cortical pathways. This condition can impair the functionality, dysregulating the system. It is a result of antipsychotics that failed to block D2 efficiently. Besides, there is very little evidence to show that cognitive deficits are an effect of hyperdopaminergia. 

Cortical impairment pathology disturbs the underlying cognitive pathways, which eventually contributes to cognitive deficits. 

Moreover, antipsychotics do not make cognition any better supporting the evidence. Treatment which results in dopamine depletion will not improve the underlying cognitive deficits.

Related: NO! Dopamine is NOT responsible for your addiction.

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