It is tempting to speculate about possible reasons for the different results of the present study and those obtained by Hoffer and Osmond, but in the end this discrepancy may best be resolved by additional research. However, one possibly important variable which future studies may attempt to control, is a hypothesized "longitudinal effect" of HHPO. That is, for possibly genetic causes, some patients may begin to produce depressant substances associated with HHPO as a defense against a growing range of cerebral augmenting - reducing condition, which displays itself in the form of perceptual instabilities. As the quantity of these depressant substances is increasing in the brain, it may gradually decrease the augmenting - reducing range of the brain, which experientially manifests itself in the form of further changing perceptual experiences. Since the HOD is sensitive to changing experiences, the patient's HOD scores would be expected to be rising temporarily. Indeed, Hoffer (1966a) found that increasing quantities of HHPO were associated with rising HOD scores.

As the quantity of these depressant chemicals increases until it has greatly narrowed the range of neurological augmenting - reducing, and then maintains an assumed steady or relatively unchanging level for an extended period of time, the resulting perceptual experiences would also be expected to be relatively unchanging. Without treatment to remove or counteract these endogenous substances for years, the patient's experiential world will, other things being constant, be relatively stable (lower HOD scores).

As stated earlier, this relatively stable perceptual state in HHPO patients is greatly distorted compared with normal perceptions, but it is not as variable or changing as in HHPO-free patients. When through appropriate treatment these depressant substances are gradually removed, or counteracted, HOD scores would be expected to increase temporarily, but if continued treatment is able to return the brain to the state of the normal augmenting - reducing range and level, then, with time, HOD scores would be expected to decrease and gradually reach levels found in normal individuals.

Unfortunately, in all HHPO-HOD-VFA studies to date, the effects of a hypothesized "longitudinal effect" of HHPO have not been controlled or investigated. It should be noted that in terms of the above hypothesized "longitudinal effect", Hoffer's and Osmond's data were obtained from patients in an "acute care facility", while the data in the present study were obtained from patients admitted to a more chronic, "long-term care facility". Most of the patients in the present study had a history of previous hospital admissions, and thus those with HHPO may have had this chemical state for years. Therefore, in terms of this "longitudinal effect", Hoffer's and Osmond's patients may have been largely acute HHPO patients undergoing a changing HHPO state "imposed" upon a wide range of cerebral augmenting - reducing, and thus could be experiencing greater perceptual instability (higher HOD scores) than HHPO-free schizophrenic patients who may also have a similar condition of neurological augmenting - reducing, but not the additional changes associated with HHPO. The present study, consisting largely of chronic patients, who may have had a relatively constant HHPO state for years, and thus a narrower range of augmenting - reducing than HHPO-free patients, would be expected to have more stable perceptions (lower HOD scores), though as shown earlier, greatly distorted due to extreme neurological attenuation of their sensory environment. Naturally, it is possible that some acute patients may stabilize their HHPO state for a period of time which could temporarily stabilize their perceptions (lower HOD scores), and some chronic patients may at times have fluctuating HHPO levels and consequently have elevated HOD scores during these periods. Therefore, it would be important to monitor both the HHPO and perceptual states over an extended period of time in the same patients. Control of this hypothesized longitudinal variable in future HHPO-HOD-VFA studies may help resolve what may only be an apparent discrepancy between Hoffer's and Osmond's data and the present study.