Skip to main content

Cognitive Impairment in Schizophrenia and the Circadian Clock

Veeha Verma

Remedial Blog Post for Quiz 6
Schizophrenia has perhaps one of the biggest impacts on cognition, leading to severe cognitive impairment. No case is exempt, the two going hand in hand. However, the factors within the illness that lead to this impairment are not well known or discussed. Due to the sleep disorganization and disruption, the role of the circadian rhythm comes into question. A prolonged disturbance in the exposure to light and dark cycles is known to have extreme effects on cognitive representation, memory and learning. We will now look at whether and what the extent of the influence of the circadian rhythm on cognitive impairment is.
                To begin lets first look at what the circadian clock and the circadian rhythm are. The circadian clock may be thought of as an endogenous clock which runs on a 24-hour cycle, the central mechanism of which is situated in the suprachiasmatic nucleus (SCN) of the hypothalamus in mammals. This rhythm of physiological and cellular processes is modulated and susceptible to external cues in the form of light, which coordinates internal time with environmental changes. The circadian rhythm is any biological process that shows “endogenous, entrainable oscillation of about 24 hours”. Sleep disturbances are a characterizing feature of schizophrenia, some believing it is more important to treat before the actual illness. On the other hand, cognitive functioning itself is closely related to the day-night cycle. The periods of sleep and wakefulness thus play a crucial role in the synchronization with the external world and temporal alignment. So how does this express itself in schizophrenia? The first signs of cognitive impairment begin to show at the very outset of psychosis. The effects of this are not localized, affecting the generalized mental faculties useful in effective negotiation of external activities. These activities could include learning, remembering, planning and strategy formation, as an effect of the specific higher mental processes being disrupted by schizophrenia - working memory, inhibition, memory consolidation and information-processing speed. Most importantly this impairment is a very strong predictor for later social and occupational dysfunction, making intervention in this field of primary importance.
                So let’s break down the exact role of the circadian clock in this. To study its affects and possible remediation, Bromundt and colleagues worked with a sample of “well-characterized” patients with schizophrenia (n=14) by having them wear actigraphs (“Actigraphy is a non-invasive method of monitoring human rest/activity cycles”) for a three-week period, while also monitoring melatonin secretion before and after sleep on several occasions throughout. Patients were entrained to the regular sleep cycle, asleep at night and awake during the day, removing the confound of gross disruptions of circadian activity frequently noted in mental health patients. Hence, circadian disturbances showed in smaller ways, with increased night activity and irregular melatonin secretion in certain patients. In cognitive tests before and after the actigraphy study, results remained mostly stable. The group with a normal circadian rhythm performed within the normal range of published data. In comparison, the group with disrupted circadian cycles performed worse on all but one of the cognitive tests (the tests used were verbal fluency, the Stroop test and the Trail Making test). Interestingly, the study showed that in all patients’ large associations between day and night activity ratio and the cognitive measures. Effect sizes were ranging from 0.66 to 0.83, however, no association between the severity of the symptoms or the duration of the illness was seen. Thus, a specific causation link is observed between abnormalities in the circadian rhythm and impairment of cognitive abilities in schizophrenia.
                The study however, has certain limitations. For instance, it doesn’t specify what it means by “well-characterized” patients. It doesn’t standardize duration of illness or the kind of schizophrenia being exhibited. Further, the sample size is quite small within itself, if then broken into sub-groups it is hard to draw conclusions on such few specimens. However, the basis of these findings appear sound and this data could have great value in the future. Follow-up studies should be conducted so that intervention on this basis can be developed. 


Bibliography:
Circadian rhythms and cognition in schizophrenia. Available from: https://www.researchgate.net/publication/51692459_Circadian_rhythms_and_cognition_in_schizophrenia [accessed May 03 2018].
Labels:

Comments

Post a Comment

Popular posts from this blog

Analysing “Anniyan”: Dissociative Identity Disorder meets Personality Disorders

Pranaya Prakash In the movie “Anniyan” (Shankar, 2005), the protagonist Ramanujam Iyengar, also known as Ambi, is the host of his alters: Remo and Anniyan. While the focus of the movie is only on Dissociative Identity Disorder (DID), also known as Multiple Personality Disorder (MPD), the host, Ambi, and the alter, Anniyan, show symptoms of Obsessive-Compulsive Personality Disorder (OCPD) and Antisocial Personality Disorder (ASPD), respectively. In this blog post, I attempt to critically analyse the portrayal of DID and the possibility of the protagonist having comorbid Personality Disorders. While it is highly unlikely for individuals with DID to have comorbidities with Personality Disorders ( Antisocial Personality Disorder ), especially with OCPD and ASPD (Fink, 1991), it is interesting to think of the possibility and analyse the developmental trajectory of these individuals.  The movie starts with the character development of Ambi, a lawyer who is meticulous and very particular ...
Post a Comment
Read more

Hardin's trauma

“After”, is a 2019 teen romantic drama directed by jenny gage that revolves around the love of  Tessa, an inexperienced teenage girl, with Hardin, a mysterious ‘bad boy’ . Hardin, the main male character, never had a secure relationship with his father. When Hardin was young, his father used to be an alcoholic with a lot of debt. When he was just eight years old, intruders broke into his home looking for his father for money, however, there was only Hardin and his mother. The intruders forced themselves on Hardin’s mother, and Hardin, who was sleeping then, came downstairs to see what was wrong. To Hardin’s shock, his mother was being raped by three men, one by one. Hardin’s mother told him to leave, however, one man forced him to watch everything.  I would assume that Hardin has PTSD as a result of this incident, and in this paper I will try to prove it. Symptoms of PTSD and scenes that prove Hardin had it: The person subsequently re-experiences the event through both intrusi...
Post a Comment
Read more

Is Patrick Jane a psychopath?

Under the Diagnostic and Statistical Manual of Mental Disorders (DSM), Psychopathy was never recognized, until the revised DSM-5 categorized it under Anti-Social Personality Disorder. “He will choose you, disarm you with his words, and control you with his presence” (Hare)  Psychopaths can replicate the behavior which the person they are interacting with thinks they want from them, without feeling a thing, which contributes greatly to their ability to manipulate. Psychopaths charm and lie their way seamlessly to the top, and while they lack empathy, they are well-liked because they know what to say and when to say it. Psychopaths occupy most of the positions of power in our society and corporations and thus often end up being glorified. This glorification of psychopaths is most evident in the portrayal of psychopathy in TV shows. Some of the most notable characters which the screen has ever seen, like Marlo Stanfield from ‘The Wire’, James Moriarty from ‘Sherlock’, Hanni...
Post a Comment
Read more