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Monday, July 30, 2018

Is there a general psychopathology factor?


In the last few decades we've witnessed a dramatic rise in the number of DSM mental disorders.  DSM1, published in 1952, included 128 mental disorders; DSM5, published in 2013, includes 541 mental disorders (Blashfield et al, 2014).  There is a high degree of comorbidity between mental disorders (comorbidity means a person having two disorders or more at the same time).  Comorbidity rates in psychiatry roughly obey the 50% rule: half of the people who meet diagnostic criteria for one disorder also meet diagnostic criteria for a second disorder concurrently; half of the people with two disorders meet criteria for a third disorder, etc.
There is also sequential comorbidity (a person overcomes one disorder and then has a second disorder).  For example, longitudinal studies show that general anxiety disorder (GAD) and depression are sequentially tied: a person who has one of them at any point in time has a higher risk of developing the second one in the future (Caspi et al, 2014).
This high comorbidity means that there may be a simpler structure to psychopathology than the one arising from the current diagnostic criteria that identify a lot of distinct and different disorders.
Albert Einstein wrote: "The supreme goal of all theory is to make the irreducible basic elements as simple and as few as possible without having to surrender the adequate representation of a single datum of experience." (Carroll, 2017).
Clinicians realize that many disorders have common dimensions/factors (these broad factors are parallel to the broad abilities in the CHC model).  Researchers identify two broad factors typical of childhood disorders:  internalizing (anxiety, depression, phobias) and externalizing (aggression, antisocial behavior,  hyperactivity-impulsivity).  We are familiar with these dimensions from the Achenbach questionnaire.  Externalizing disorders usually begin in childhood and affect boys more than girls, while internalizing disorders appear more towards adolescence and are more typical of girls.  Some scholars find that internalizing subsumes two lower-order factors: distress (major depression, generalized anxiety, dysthymia) and fear (agoraphobia, social phobia, specific phobia).  Externalizing and internalizing continue to characterize personality throughout life.  In adults some researchers add an additional broad factor:  thought disorders.  This factor correlates 0.6 with internalizing (Caspi et al, 2014).
Externalizing and externalizing correlate 0.4-0.6, but researchers treat them as two separate broad factors.  Are they really so, or are they two extremes of the same dimension?  Intuitively we feel that a person who has high externalizing will tend to be low in internalizing and vice versa.  It's possible that the positive and significant correlation between internalizing and externalizing indicates the existence of a superordinate common factor, a general psychopathology factor (p, analogous to g, general intelligence).  As g reflects the correlation between broad cognitive abilities, p might express the correlation, the common variance, between different dimensions of psychopathology (Caspi et al, 2014).
I have reservations about the name "general psychopathology factor".  What's the use of emphasizing pathology? According to this formulation, the higher a person's p, the poorer his mental health.  Beyond the bad feeling this evokes, the p factor correlates negatively with g.  It might have been better to name this general factor on the positive side, say a "general mental health factor", h.
One more thing:  I think there is room for unification:
a. A unification between conceptualizations of the broad factors of psychopathology (internalizing, externalizing, thought disorders) and conceptualizations of personality (for example, the BIG5 model).  Internalizing may be linked to Neuroticism (and also to Agreeableness and Conscienciousness); Externalizing may be linked to Extraversion and to Openness to experience, and a thought disorder factor may also be linked to the Openness factor (at its extreme).  As will be seen later, the broad factors of psychopathology affect and are affected by the BIG5.
B.  A unification between conceptualizations of personality/psychopathology and conceptualizations of cognitive abilities.  I think personality includes both traits, broad factors of psychopathology and cognitive. The tight linkage between conscientiousness and executive functions attests that.
The studies discussed below examined three possible models of mental health/psychopathology in children, adolescents and adults:
A.  a model of several correlated broad factors (internalizing, externalizing and, in adults, thought disorders).  Each factor expresses the common variance (the common element) of the mental disorders that are mapped to it.  This model is presented in figure 1.

Figure 1: a model of several correlated broad factors
B.  a bifactor model, that sees psychopathology as having two aspects: 1) several broad factors (internalizing, externalizing and, in adults, maybe also thought disorders).  Each factor expresses the common variance (the common element) of the mental disorders that are mapped to it. 2) a general psychopathology factor – that expresses the common variance of all mental disorders.   This model is presented in figure 2.

Figure 2: a bifactor model
C.  a model with one general psychopathology factor that expresses the common variance of all mental disorders.  This model is presented in figure 3. 
Figure 3: a model with one general psychopathology factor
In a previous post we discussed distinctions between such models as related to cognitive abilities.

Research with children: The three models were compared by Martel et al in 2017.  Brazilian families were screened at schools on the registry day (the average age of the children was 9 and the average age of the parents was 35).  Out of about 8000 families the researchers identified about 1500 families with high risk for mental disorders and 950 families with no such risk.  The parents were asked about symptoms of depression, mania, phobias, anxiety, panic, OCD, psychosis, addictions, ODD and CD in one or more of the child's first degree relatives. The child's psychopathology symptoms (panic attacks, phobias, anxiety, eating disorders, depression, PTSD, OCD, CD, ODD, ADHD and ASD) were assessed with interviews and questionnaires given to the parents.    
The model most fitting with the childrens', the fathers' and the mothers' data was the bi-factor model that contained a general psychopathology factor and three broad factors:  fear, distress and externalizing.  Fear and distress were highly correlated (0.861).  P explained most of the children and adults' item variance.
There was a significant correlation between the mother's p and the child's p as well as between the father's p and the child's p.  There was a significant correlation between the mother's p and the child's distress and fear factors.  The same was true in respect to the father.  The mother's externalizing factor was significantly related to the child's p and to the child's externalizing factor.  The father's externalizing factor was related to the child's externalizing factor, and negatively related to the child's fear factor.  All correlations were 0.33 and below.
Research with adolescents was done in 2015 by Patalay et al (one of the researchers was Peter Fonagy).  The researchers gathered data from about 23500 children aged 11-13, in 7th and 8th grades, from 200 schools in Britain.  After a year the mental state of about 10300 of the children was re-assessed.  In addition to that, about 7500 children who were in 8th grade at the time of the first assessment had taken a national achievement test a year and a half later.  Thus the researchers were able to assess the influence of psychopathology on achievement.  It should be noted that the group of children who were reassessed and who took the achievement test contained less boys and less children of lower SES.  
During both assessment times the children filled two computerized questionnaires ('Me and My school'; Strengths and Difficulties Questionnaire SDQ).
In this study too, model B, the bifactor model (seen in figure 4) best explained the data.  Model A with only two broad factors (internalizing and externalizing) fit the data almost as well.  In model A, the correlation between internalizing and externalizing was 0.45, while in model B, the bifactor model, the correlation between internalizing and externalizing was small and negative (-0.16).  This is reasonable, since after accounting for p, each of these broad factors expresses only its unique aspect. Consequently the correlation between them is significantly lowered.  The p factor was correlated 0.3 with internalizing and 0.22 with externalizing. 

Figure 4: the bi-factor model, Patalay et al, 2015.
The p factor predicted psychopathology, future internalizing and externalizing and future academic achievement.  Both externalizing and internalizing factors from model A predicted future psychopathology and future academic achievement.  The size of the effect of the P factor in predicting future psychopathology was large; externalizing and internalizing had a  small to moderate effect size in the prediction of future psychopathology.
A study with adults was done by Avshalom Caspi, Terrie Moffitt and their colleagues in 2014.  They used data from a longitudinal study, the Dunedin study, which follows about 1000 people born in Dunedin, New Zealand.  These people were repeatedly assessed since the age of 3 (they were last assessed at the age of 38).  The data brought here were gathered when the participants were 21,26,32 and 38 years old.
At each assessment period the participants were asked about symptoms they had during the past year (symptoms of alcoholism, drug abuse, conduct disorder, depression, general anxiety disorder, fears/phobias, OCD, mania and symptoms of schizophrenia).  The researchers also asked whether during the period between assessments the participants took psychiatric medicine or were in psychiatric hospitalization.
in this study too, the model that best explained the data was the bi-factor model, with a general psychopathology factor and two broad factors (internalizing and externalizing).  Model A, which had three broad factors (internalizing, externalizing and thought disorders) fitted the data almost as well.
The p factor was extracted in all ages (21,26,32, and 38).  The correlation between the p factor and externalizing was 0.637; the correlation between the p factor and internalizing was 0.917 (!).   Another broad factor, thought disorders, had a near perfect correlation (0.997) with p, which attests to their being almost identical.
According to Caspi and his colleagues, "Any individual who carries a strong General Psychopathology liability might, if their disorder grows severe enough, experience psychotic thought processes, whatever the presenting diagnosis; that is, unwanted irrational thoughts are not just for the formal psychoses. Cognitive behavioral therapies aimed at correcting patients’ inaccurate thoughts are among the most effective treatments for a wide variety of disorders. The clinical literature is replete with discussion of disordered thought processes in the context of affective disorders, anxiety disorders, eating disorders, autism, posttraumatic stress disorder, somatoform disorders, dissociative disorders, identity disorders, personality disorders, and substance disorders. Most chapters of the DSM mention thought symptoms. Indeed, in general, the only disorders lacking prominent focus on disordered thought in their symptom criteria are disorders of childhood".
Caspi et al found a positive correlation (0.3) between externalizing and internalizing in model A, but a negative correlation (0.47-) between these two factors in model B.  The positive correlation in model is and indication of the general psychopathology factor.  After accounting for p, people who tend towards externalizing behaviors (for example, drug abuse or antisocial behavior) tend less towards internalizing behaviors (depression, anxiety) and vice versa. 
Men leaned more towards externalizing and women leaned towards internalizing.  There was no difference between the sexes in thought disorders.  In model B there were no differences between the sexes in the tendency towards general psychopathology.
Links to the BIG5
In Caspi et al's study, each of the three factors from model A was significantly associated with low Agreeableness, low Conscientiousness, and high Neuroticism.  General Psychopathology was distinctly characterized by high Neuroticism and low Agreeableness and Conscientiousness.  High- p individuals experience difficulties in regulation/control when dealing with others, the environment, and the self.
Individuals who score high on a liability to Externalizing disorders, net of a tendency toward General Psychopathology, have poorer impulse control (low Conscientiousness); can be aggressive, rude, and manipulative (low Agreeableness); but also evoke and enjoy social attention and appear to be sensitive to potential rewards (high Extraversion). In contrast, individuals who score high on a liability to Internalizing style disorders, net of General Psychopathology, are more easily distressed (high Neuroticism) and tend to refrain from actively approaching, engaging, or exploring their environment (low Extraversion), although they tend to be agreeable.
 Links to intelligence:
Adults with higher levels of p scored lower on an IQ test than their age peers with lower levels of p.  Adults with higher levels of p fared less well on tests requiring attention, concentration, mental control, visual-perceptual speed, and visual-motor coordination. People who knew them well said that individuals with high levels of p experienced cognitive problems in their everyday lives.
General insights:
Studies with children, adolescents and adults show the existence of a bifactorial structure of psychopathology/mental health.  The structure includes a general psychopathology factor and two broad factors (internalizing and externalizing). 
Parent maltreatment in childhood raises the risk for a high p.  Impaired language development and cognitive development in childhood, poor executive functions and poor impulse control in childhood are risk factors for a high p in adulthood.  A family history of psychiatric disorders also raises the risk for higher general psychopathology. 
The p factor influences the BIG5 traits and is influenced by them.  The p factor is related to lower general intelligence.
Caspi et al write: "there could be a developmental progression of severity in psychopathology. Many individuals manifest a brief episode of an individual disorder, a smaller subset of individuals progress to develop a persistent Internalizing or persistent Externalizing syndrome, whereas only a very few individuals progress to the extreme elevation of p, ultimately emerging with a psychotic condition most likely during late adolescence or adulthood".
"Such a developmental progression would require …that brief episodes of single disorders are widespread in the population, which is …supported by research.  A developmental progression also would require that individuals who manifest psychosis have an extensive prior history of many other disorders, which has been reported. In addition, a developmental progression would anticipate that when individuals are followed long enough, those with the most severe liability to psychopathology will tend to move in and out of diagnostic categories. Today’s patient with schizophrenia was yesterday’s boy with conduct disorder or girl with social phobia… This developmental progression hypothesis is consistent with evidence that sequential comorbidity is the rule rather than the exception and that individuals experiencing sequentially comorbid disorders also exhibit more severe psychopathology".
"…Parallels can be drawn with immuno-deficiencies in physical health. Immunocompromised individuals are more susceptible to infections. Identifying the immunodeficiency rather than just observing the expressed symptoms is crucial to the long-term management and treatment of individuals with these immune deficits. Similarly, the general psychopathology factor places the emphasis on considering the individual’s inherent propensity for psychopathology, rather than simply focusing on diagnostic categories and symptoms. The existence of a general psychopathology factor or deficit suggests that individuals with greater propensity (or higher general psychopathology) are more likely to experience psychopathology no matter what, with environmental factors and life events perhaps serving only as moderators and triggers of the expression of specific disorders".  Identifying the p factor, even in children, may help to give the child preemptive interventions, like parental guidance and assistance in building emotional regulation skills.
Blashfield, R. K., Keeley, J. W., Flanagan, E. H., & Miles, S. R. (2014). The Cycle of Classification: DSM-I Through DSM-5. Annu. Rev. Clin. Psychol10, 25-51.
Caspi, A., Houts, R. M., Belsky, D. W., Goldman-Mellor, S. J., Harrington, H., Israel, S., ... & Moffitt, T. E. (2014). The p factor: one general psychopathology factor in the structure of psychiatric disorders?. Clinical Psychological Science2(2), 119-137.
Carroll, S. (2017). The big picture: on the origins of life, meaning, and the universe itself. Penguin.
Martel, M. M., Pan, P. M., Hoffmann, M. S., Gadelha, A., do Rosário, M. C., Mari, J. J., ... & Rohde, L. A. (2017). A general psychopathology factor (P factor) in children: Structural model analysis and external validation through familial risk and child global executive function. Journal of abnormal psychology126(1), 137.  https://pdfs.semanticscholar.org/ce68/6315f65d19842a226063d861d4a80b213cce.pdf
Patalay, Praveetha, Peter Fonagy, Jessica Deighton, Jay Belsky, Panos Vostanis, and Miranda Wolpert. "A general psychopathology factor in early adolescence." The British Journal of Psychiatry 207, no. 1 (2015): 15-22.
https://cloudfront.escholarship.org/dist/prd/content/qt40f4m10p/qt40f4m10p.pdf

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