Olaf Fjetland: Programming CODE-DD

In 1989, Thomas A. Ban published CODE-DD, Composite Diagnostic Evaluation of Depressive Disorders. The same year, while working with Tom in the Vanderbilt University Department of Psychiatry, I wrote and released an interactive computer program based upon the main component of the book, the Semi-Structured Interview for Depressive Disorders (SSIDD).

The SSIDD consists of 90 question sets, with each set corresponding with one variable characteristic of depressive illness. Those variables are found in the 90-item Rating Scale for Depressive Diagnoses (RSDD) and its subscale, the 40-item Rating Scale for the Assessment of Severity in Depressive Disorders (RSASDD). Thus, when the computer-assisted interview is completed, physicians have results which not only point to a diagnosis, but the severity surrounding that diagnosis, too.

The RSDD emerged out of Tom's years-long, painstaking research into the development of 25 diagnostic systems, from Krapelin's late 19^th to early 20^th century "Criteria of Depressive States and Depressive Excitement" to the 1987 "DSM-III-R Criteria of Depressive Disorders." Scoring the results of the SSIDD produced a diagnosis for each of these 25 systems based on their specific criteria.

Out of necessity, I had learned Fortran IV (released in 1962) "on-the-job" in order to use the Biometric Laboratory Information Processing System (BLIPS) of the Early Clinical Drug Evaluation Units (ECDEU). It was my "language" of choice, even though numerous updates to Fortran IV had been made and new languages such as Cobal, Pascal and C++ had been introduced, because it was the only programming language I knew, having never taken an organized programming class.

Programming the SSIDD began, simply, because it was ideal for the purpose. The semi-structured interview is based on "decision trees," a core component of software design. The interview was conceived to elicit "yes" or "no" answers and contained built-in guidance for proceeding through it: if the answer is yes, go here or there, if no, go somewhere else, eventually coming to a "stop" when the criteria for a diagnosis in the 25 component diagnostic system algorithms had been met. Later, I discovered that there were no other computerized psychiatric interviews in existence at the time.

Once written, the CODE-DD software was introduced to a core group of physicians with whom I met in Hungary and taught how to use the system. Essentially, all they had to do was turn it on, get it running, follow the screen prompts while administering the SSIDD and print out the results. It was a simple program which, in essence, captured more than 100 years of diagnostic conceptualization given voice by Tom Ban.

Since I am not a physician, I never "used" the program during a psychiatric interview. However, during the writing and debugging of the software, I "conducted" thousands of "interviews." Once perfected, the software never failed to achieve its purpose.

June 8 2017