The most common physical complications are epilepsy and more or less marked residuals of infantile cerebral paralysis.

In some cases the epilepsy, in the course of years, produces mental deterioration, and the imbecile or moron becomes, in addition, an epileptic dement.

Among mental complications are to be noted acute or subacute episodes which appear in various clinical forms: maniacal excitement, depression, sometimes delusions more or less imperfectly systematized. Often the mental disorders appear as exaggerations of a constitutional anomaly, essentially a function of the patient's make-up. An individual habitually touchy and suspicious develops persecutory delusions, another habitually psychasthenic suffers an attack of depression, etc. Such episodes in imbecility are incontestable clinical realities, and nothing is more justifiable than, for instance, a diagnosis of maniacal excitement in an imbecile. Unfortunately it is very difficult to assign for such episodes a place in psychiatric nosography. Do they constitute mental disorders peculiar to imbecility? Are they not, on the contrary, periodic psychoses to which the imbecility merely imparts special features: mobility of the symptoms, childish character of the delusional conceptions? For our part we are rather inclined toward the second hypothesis. In fact a full series of transition cases leads from classical manic-depressive psychoses to the more typical attacks in imbeciles. Moreover, such attacks in imbeciles present the same tendencies toward recovery and toward recurrency.

It must be noted, however, that the influence of external causes, psychic as well as physical, in bringing about recurrencies, appears to be more marked in imbeciles than in manic-depressive persons who are not defective. It is also to be noted that the effect of suggestion upon the mental symptoms is surely more pronounced in the psychoses of imbeciles than in ordinary types of recurrent psychoses, so that psychic treatment is here found to be more efficacious.


In the diagnosis of arrests of development certain precautions and certain practical requirements should be borne in mind.

It should not be made on incomplete evidence. Illiteracy, or gross ignorance, or dependency, or low social status ("a common laborer all his life," "of the domestic servant class ") may arouse suspicion of mental defectiveness but would not suffice to establish it, being often largely accounted for by environmental conditions. Similarly, a poor showing in psychological tests would not suffice for a diagnosis, but might lead to mistaking temporary psychotic disability or acquired mental deterioration for original defect. The diagnosis must be based on a complete psychiatric investigation following some such scheme as that outlined in Chapters V and VI, Part I, of this Manual, and including family history, personal history, history of present disorder, physical examination, mental examination, and such special diagnostic procedures as may be indicated.

The diagnosis being established, it is necessary for practical purposes to determine the degree and nature of the mental defect. In the management of a given case it is obvious that much will depend on whether it is one of totally helpless idiocy; or low, medium, or high grade imbecility; or low, medium, or high grade moronism; or borderline intelligence with possibly considerable general educability or good capacity in some limited directions. The application of psychological measurements is here of great assistance. Similarly, it is important to determine whether the patient's difficulties are attributable mainly or largely to defect of intelligence or to unruliness, eroticism, lack of emotional control, criminal tendency, or other temperamental anomaly. The social history or several weeks of direct observation should be helpful in clearing up these questions.


In cases of arrest of development no recovery is, of course, to be looked for; but much can be accomplished in a practical way, as the student may judge from the following discussion of treatment.