Positive & Negative Symptoms of Schizophrenia

 

Schizophrenia is a severe mental illness with both positive and negative symptoms. The actual term “schizophrenia” means “split mind”, but schizophrenics do not have multiple personalities. Eugen Bleuler, the man who created the word, intended its use to mean “a break from reality caused by disorganization of the various functions of the mind (Carlson, 2004).” There are many types of schizophrenia including: paranoid, hebephrenic, catatonic, undifferentiated, residual, and simple schizophrenia, to mention a few. All have certain dominant features, but share the same common symptoms (Mental Health, 2005).

When one hears the word positive, he or she most likely thinks of something that is        good or helpful. This is definitely not the case in schizophrenia. The term “positive symptoms” refers to symptoms that are easily recognized by their presence. One        positive symptom, and likely the most prominent of schizophrenia, is thought disorder. Schizophrenics have difficulty in arranging their thoughts in a logical pattern. They       often jump from one topic to another and form irrational conclusions. To a schizophrenic student, the conclusion that he or she received a bad grade because aliens graded his or her paper would make as much sense as the conclusion that he or she did a poor job. While holding a normal conversation, you will often hear one of these individuals  muttering irrelevant words or rhyming words instead of choosing words that actual describe what they are speaking about. Another positive symptom is delusions.    Common delusions might include the following: someone is trying to kill them; they     have supernatural powers; or radars have been placed inside of their head to control them. Hallucinations, which can be caused by drugs such as LSD, occur naturally in schizophrenics. Auditory hallucinations are most common, but some individuals also    have visions. You will often hear patients say they have “voices in their head” instructing them to do something, reprimanding them, or rattling irrelevant phrases. Olfactory hallucinations are also frequent. Many times patients will have the delusion that someone is trying to kill them with poison gas (Carlson, 2004). One of the main positive symptoms of hebephrenic schizophrenia is incongruous mood, or a shallow, inappropriate mood which can consist of constant giggling, smiling, grimaces, or pranks. Catatonic schizophrenics have a positive symptom of increased motor function that is non-related  to stimuli around them. Of course, many people think of catatonic individuals as nonmoving or functioning, and while schizophrenic catatonics do experience long periods of inactivity and stupor, violent outbursts and inappropriate motor activity also occurs (Mental Health, 2005).

The term “negative symptoms” refers to the absence of typical behavior. For instance, schizophrenics will often have severe apathy, or indifference, lack of emotion, or lack of interest about important matters. When speaking about anything emotional, they may speak with a monotone voice. When experiencing positive symptoms, patients may be very talkative, whereas experiencing negative symptoms will cause a patient to say very little. Also, individuals will have difficulty in feeling any type of pleasure. More often than not, these negative characteristics will cause a patient to be withdrawn from others and have little social interaction. It should be noted that these symptoms cannot be due to depression or drug abuse to be classified as true negative symptoms of schizophrenia. Many times these symptoms will be overlooked opposed to positive symptoms that are more apparent. One is more likely to notice if someone is talking to a person who isn’t there opposed to someone being quite or unemotional. Consequently, the social life of     a schizophrenic will often wane considerably when only the positive symptoms of the disorder are noticed treated.

The biological basis for positive and negative symptoms in schizophrenia is as different   as the actual symptoms themselves. There are many different variations on the hypothesis for the biological cause of positive symptoms, but all theories lead back to   one central point: the role of dopamine. Many scientists believe that schizophrenics have hyperactivity of dopaminergic synapses, most likely in the mesolimbic pathway that links the ventral tegmental area (located in the midbrain and rich in dopamine and serotonin)   to the nucleus accumbens and amygdala (parts of the limbic system). What first gave researchers the hypothesis that dopamine was linked to positive symptoms in schizophrenia was the analysis of antipsychotic medication. All of the antipsychotic medications had one thing in common: they blocked dopamine receptors. In comparison, drugs such as cocaine, amphetamine, and methylphenidate worked as dopamine agonists and would produce the positive symptoms. Antipsychotic medications would also relieve the symptoms found in drug users. This pharmaceutical examination brought researchers to the conclusion that increased dopamine production, neurons sensitive to dopamine, or the slow absorption rate could possibly cause the aforementioned positive symptoms. Patients with greater amounts of dopamine have shown greater positive symptoms,   which would support the theory that dopamine is increased in schizophrenics. Other studies have tried to find evidence of an increased number of dopamine receptors, but results have been mixed. It is probably a farfetched idea that this is the primary basis for the disorder. Because drugs that function as agonists reinforce behavior, positive symptoms might be caused by reinforcement of behavior at the wrong moments. For instance, schizophrenics often feel “great” at the beginning of an episode; this euphoric feeling is most likely caused by increased activity of dopaminergic neurons. Other symptoms, such as delusions and hallucinations, are not so wonderful. Presumably,    since dopamine is thought to be an important part of the reinforcement process and dopamine levels are increased when a patient has positive symptoms, the patient may think that these responses are normal and acceptable. The amygdala, which is known    for its correlation with emotional responses, is thought to bring about delusions when overstimulated with dopamine.

The negative symptoms of schizophrenia are thought to be caused by brain  abnormalities. The majority of patients have neurological difficulties, such as unusual   facial expressions and poor eye movement control. Studies have shown that the normal ventricle size of a schizophrenic patient is twice as large as in control groups. CT and MRI scans have also shown loss of brain tissue, which most likely accounts for the enlarged ventricle size. Everyone loses a little brain tissue as they age, but schizophrenics have a more rapid  loss. Also, brain abnormalities are known to exist in the medial temporal  lobes, frontal lobes, lateral temporal lobes, parietal lobe, basal ganglia, thalamus, corpus callosum, and maybe even the cerebellum. Decreased activity of the frontal lobes is   known as hypofrontality. This decline in action, particularly in the dorsolateral prefrontal cortex, may be another cause of the negative symptoms. Although the positive and negative symptoms of schizophrenia are so different, studies have shown they may actually be related. The aforementioned decreased activity may be caused by a decline in dopamine in the prefrontal cortex. This may sound strange since the increase of  dopamine has been known to cause positive symptoms in schizophrenia, but research on certain drugs have helped to shed light on this topic. For instance, schizophrenics usually perform poorly on neurological tests (specifically for prefrontal cortex damage) but when given amphetamine, the blood flow in the dorsolateral prefrontal cortex increases, as well as their performance on the test. In addition, PCP addicts will experience negative symptoms due to a decline in the metabolic activity of the frontal lobes. It has also been found that PCP decreases the amount of dopamine the dorsolateral prefrontal cortex creates, and behavioral impairment directly correlates with this dopamine decrease. Thus, the decreased dopamine production creates the hypofrontality of the frontal lobes, which further creates the negative symptoms of schizophrenia. Some researchers think that the decreased prefrontal activity actually causes hyperactivity in the mesolimbic dopamine pathway. Neurons located in the prefrontal cortex send axons to the ventral tegmental area. The axons then form synapses with neurons that secrete GABA (an inhibitory neurotransmitter) which is transmitted to the nucleus accumbens. When the prefrontal cortex is electrically stimulated, the release of dopamine declines in the nucleus accumbens. In other words, if the opposite is true then the decline of activity in the prefrontal cortex would lead to an increase of dopamine release in the nucleus accumbens. Clozopine, an atypical psychotic, successfully relieves negative and positive symptoms and increases dopamine release in the prefrontal cortex, while decreasing dopamine release in the nucleus accumbens. All these neurological responses point to one hypothesis: a domino effect. Hypoactivity of dopamine in the prefrontal cortex causes hypofrontality, which results in negative symptoms of schizophrenia. Furthermore, the hypofrontality causes an increase of dopamine release in the prefrontal cortex, which accounts for the positive symptoms of schizophrenia (Carlson, 2004). Studies of bipolar disorder, which has many similarities to schizophrenia, have also coincided with this theory. Researchers propose that a dopamine decrease may be responsible for the depression stages, while a dopamine increase may be responsible for the manic stages (Lundbeck, 2005).

In conclusion, schizophrenia can be a debilitating illness with both positive and negative symptoms. While having positive symptoms, a patient may be overly active, but have  very poor and scattered judgment, along with delusions and hallucinations. While having negative symptoms, a patient may lose all sense of pleasure and be overly withdrawn. Both of these symptoms can cause great social difficulties. People often find schizophrenics difficult to be around in the positive stages because of their off the wall ideas, and schizophrenics do not want to be around others when experiencing negative symptoms. Scientists have hypothesized that the negative symptoms are caused by   brain abnormalities and the positive symptoms by hyperactivity of dopamine release. These are thought to be related; the decrease of dopamine in the prefrontal cortex indirectly causes the increase of dopamine in the nucleus accumbens. Further research   on this topic may explain the reasons some disorders share many of the same  symptoms, and also bring forth new methods of treatment.
References:

1. Carlson, Neil R. (2004). Vision. In Physiology of Behavior, 8, 182-183.

2. Health Matters. (2005). Schizophrenia. Retrieved March 5, 2006, from http://www.mental-health-matters.com/disorders/dis_details.php?disID=84

3. The Lundbeck Institute. (2005). Aetiology. In Bipolar Disorder.                          Retrieved March 6, 2006, from http://www.brainexplorer.org/bipolar_disorder/Bipolar_Disorder_Aetiology.shtml