High-functioning patients with schizophrenia experienced “mind-pops” significantly more often than did two control groups in a preliminary study exploring a possible connection between these benign cognitive phenomena and hallucinations, according to a report published online in Psychiatry Research.

Mind-pops is the term coined in 1997 for the involuntary semantic memories that “come to mind unexpectedly, without any attempt to recall them, and consist of isolated fragments of one’s semantic knowledge, rather than meaningful episodes from one’s personal past.” They typically occur when a person is alone, involved in an everyday activity that requires little attention (such as brushing teeth), and thinking about unrelated matters (such as what to wear that day), and they consist of the sudden intrusion of a word or phrase, a name, a visual image, or a familiar snatch of music that “amazes the person with its irrelevance to the current situation,” said Ia Elua, Ph.D., of the University of Herefordshire School of Psychology, Hatfield (U.K.), and her associates (Psychiatry Res. 2012 [doi:10.1016/j.psychres.2011.11.026]).

Mind-pops usually are “one-off occurrences,” but occasionally they can come to mind repeatedly and be difficult to dismiss. Musical mind-pops – recurring melodies, songs, or commercial jingles – “have been recently studied under a variety of names such as ‘earworms,’ ‘stuck song syndrome,’ or involuntary musical imagery,” the investigators noted.

Mind-pops are different from other involuntary cognitive phenomena described in the literature in that they have no trigger. In contrast, ordinary autobiographical memories can pop up (rather than being summoned intentionally) in response to a relevant trigger – such as remembering a holiday trip when seeing an advertisement for vacations. And more intrusive memories of negative events, such as remembering being mugged when hearing footsteps approaching in the dark, also have obvious triggers.

Mind-pops usually are “one-off occurrences,” but occasionally they can come to mind repeatedly and be difficult to dismiss.
Mind-pops also differ from other cognitive intrusions such as repetitive negative thoughts, compulsions, and flashbacks of traumatic experiences in that they are benign. They usually take the form of words or phrases and less often involve visual images or music.

There are several traits common to both mind-pops and hallucinations. Both occur unexpectedly, have no triggers, and can be disruptive, hence both can sometimes be perceived as “alien” thoughts being imposed on the mind from outside. Both can sometimes occur during altered states of consciousness, such as when falling asleep or waking, but primarily occur when the individual is alone and engaged in an undemanding activity. And like mind-pops, hallucinations are primarily verbal but can also be visual or musical, Dr. Elua and her colleagues said.

These similarities led the researchers to hypothesize that mind-pops “could be the raw cognitive material from which hallucinations are constructed in schizophrenia.” To test this hypothesis, they assessed the frequency and nature of mind-pops in 37 high-functioning patients with schizophrenia and 31 high-functioning patients who had major depressive disorder without psychotic features, all of whom were attending either day treatment or outpatient mental health clinics, as well as 31 nonclinical control subjects.

The 19 men and 18 women with schizophrenia had paranoid type (23 subjects), undifferentiated type (11 subjects), or residual type (3 subjects).

All the study participants with schizophrenia said they had experienced mind-pops. In contrast, six (19%) of the subjects with depression and five (16%) of the nonclinical control subjects said they had never experienced mind-pops. This difference is statistically significant, the investigators said.

Patients with schizophrenia also experienced mind-pops more frequently than did the control subjects, scoring a median of 6.05 on an 8-point scale in which 1 signified only a few mind-pops over the lifetime and 8 signified 3 or more mind-pops per day. In contrast, patients with depression scored a median of 3.74 on this scale and the nonclinical controls scores a median of 3.13.

These results were not materially changed in further analyses that controlled for subject age and years of education, nor in an analysis that excluded all subjects who had never experienced mind-pops.

The patients with schizophrenia were divided among those who were having hallucinations near the time of the assessment (22 subjects) and those who were not having hallucinations currently but had had them in the past (15 subjects). The mean frequency of mind-pops was higher among patients who had current hallucinations, but the difference did not reach statistical significance.

In addition, patients with schizophrenia reported having a significantly larger range of the different types of mind-pops than did subjects in both control groups.

Schizophrenia patients also were much more likely to provide examples of their mind-pops in answer to an optional question. However, the content of mind-pops was similar across all three study groups.

These findings suggest “a possible intriguing link between mind-pops and hallucinations.” It may be that “ordinary mind-pops, experienced as benign phenomena by nonclinical individuals, will take the exaggerated and abnormal form of auditory and other types of hallucinations in patients with schizophrenia,” Dr. Elua and her associates said.

Future research should attempt to ascertain “whether the content of mind-pops is more negative and distressing in patients with schizophrenia than in clinical and nonclinical controls, and whether schizophrenia patients are more likely to actively suppress and/or control the occurrence of their mind-pops. If that is the case, then these processes can be responsible for transforming ordinary mind-pops into hallucinations,” the investigators said.

Alternatively, it might be that the content of mind-pops is similar between schizophrenia patients and controls, but that the schizophrenia patients interpret them as being more alien or threatening. “They may assume that something strange is happening to them … that they are ‘going mad,’ ” the researchers said.

Dr. Elua is now with the Jewish Board of Family and Children’s Services, Outpatient Mental Health Clinic, New York.