The Tree-Drawing Test (TDT, Koch’s Baum Test) is a projective psychological examination often used for assessing personality in the developmental age [
We evaluated consecutive outpatients referred over a year’s period by their relatives and physicians or who spontaneously presented themselves to the Cognitive Disorders Center of IRCCS Istituto delle Scienze Neurologiche of Bologna and to the Cognitive Disorders Center of the General Hospital of Imola, Italy. All subjects gave their informed consent to the study according to the Declaration of Helsinki. Patients were classified as demented or not according to DSM-IV-TR criteria [
All patients and controls were requested to draw a tree on an A4-sized white paper sheet with a pencil. Instructions were as follows: “Draw a tree, as you like.” No limits of time were given. The tree drawn was evaluated qualitatively (presence of crown, roots, branches, leaves, and flowers; types of trunk-end-opening, i.e., the top-end of the trunk, closed, opened, or wider than trunk) and quantitatively (height and width of trunk, crown, roots, and the trunk’s tilt). The qualitative analysis of trunks, crowns, and branches included also the characterization of the shape (single or double lines for trunk and branches; open or closed crown). Heights and widths were obtained directly in millimeter units according to the criteria shown in Figure
The Tree-Drawing Test: measurement of the height and width of crown, roots, and trunk.
Data were analyzed using the SPSS statistical analysis software, version 21.0. We performed a descriptive analysis of the various parameters of the patient groups; the comparisons of variables of various groups of the patients were obtained employing the multivariate general linear model with Bonferroni’s correction with the significance level set at
118 AD patients, 19 FTD, 46 VD, 132 MCI, and 90 controls were enrolled. Mean age, education, sex distribution, and disease duration of each group are listed in Table
Clinical data of patients and controls.
AD | FTD | VD | MCI | Controls | |
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Age |
76.73 ± 5.12 | 73.16 ± 7.87 | 77.2 ± 4.86 | 76.12 ± 5.65 | 75.11 ± 8.71 |
Sex |
34/84 | 10/9 | 24/22 | 60/72 | 32/58 |
Education |
5.61 ± 3.1 | 6 ± 2.66 | 5.85 ± 3.04 | 5.6 ± 3.15 | 6.69 ± 3.18 |
Dominance |
116/2 | 19/0 | 46/0 | 125/7 | 85/5 |
Disease duration |
2.17 ± 0.99 | 1.84 ± 0.83 | 2.17 ± 0.85 | 1.36 ± 0.54 | — |
Qualitative characteristics of trees drawn by patients and controls are listed in Table
Qualitative characteristics of trees.
AD | FTD | VD | MCI | Controls | |
---|---|---|---|---|---|
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Trunk shape |
s: 23 (19%) |
s: 2 (11%) |
s: 8 (17%) |
s: 11 (9%) |
s: 5 (6%) |
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Trunk end opening |
0: 102 (86%) |
0: 19 (100%) |
0: 43 (93%) |
0: 124 (94%) |
0: 82 (91%) |
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Crown shape |
o: 86 (73%) |
o: 12 (63%) |
o: 33 (72%) |
o: 106 (80%) |
o: 53 (59%) |
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Branches shape |
s: 84 (71%) |
s: 11 (58%) |
s: 30 (65%) |
s: 101 (77%) |
s: 53 (59%) |
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Leaves | 24 (20%) | 5 (26%) | 9 (20%) | 41 (31%) | 28 (31%) |
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Flowers | 0 | 0 | 2 (4%) | 6 (5%) | 4 (4%) |
Overall considering heights and widths of trunks, crowns, and roots of trees drawn by patients, significant differences emerge (Table
Quantitative analysis of trees and significant differences between groups.
AD | FTD | VD | MCI | Controls | Controls versus | AD versus | FTD versus | VD versus | |||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Mean ± SD | Mean ± SD | Mean ± SD | Mean ± SD | Mean ± SD | AD | FTD | VD | MCI | FTD | VD | MCI | VD | MCI | MCI | |
MMSEc | 17.61 ± 3.89 | 18.68 ± 6.42 | 19.52 ± 3.28 | 26.09 ± 1.77 | 28.04 ± 1.42 | **** | **** | **** | **** | n.s. | *** | **** | n.s. | **** | **** |
Trunk-to-crown ratio | 12.62 ± 7.59 | 12.75 ± 4.91 | 12.29 ± 6.12 | 11.04 ± 5.37 | 8.35 ± 3.72 | **** | ** | *** | *** | n.s. | n.s. | n.s. | n.s. | n.s. | n.s. |
Crown ratio | 1.51 ± 0.61 | 1.63 ± 0.57 | 1.68 ± 0.73 | 1.53 ± 0.45 | 1.45 ± 0.48 | n.s. | n.s. | * | n.s. | n.s. | n.s. | n.s. | n.s. | n.s. | n.s. |
Tree size-relative-to-page space | 0.03 ± 0.03 | 0.13 ± 0.11 | 0.1 ± 0.68 | 0.08 ± 0.06 | 0.23 ± 0.19 | **** | **** | **** | **** | **** | **** | **** | n.s. | **** | * |
Tree height | 52.09 ± 24.04 | 109.89 ± 38.98 | 91.41 ± 28.35 | 80.77 ± 28.87 | 132.61 ± 57.81 | **** | ** | **** | **** | **** | **** | **** | * | **** | ** |
Tree width | 35.86 ± 21.14 | 70 ± 39.08 | 65.43 ± 26.86 | 56.67 ± 25.6 | 96.57 ± 41.67 | **** | **** | **** | **** | **** | **** | **** | n.s. | * | * |
Trunk height | 26.64 ± 15.34 | 56.74 ± 22.83 | 45.87 ± 21.11 | 38.11 ± 17.71 | 52.73 ± 23.74 | **** | n.s. | n.s. | **** | **** | **** | **** | * | **** | * |
Trunk width | 8.13 ± 7.25 | 13.58 ± 10.32 | 11.02 ± 7.99 | 9.85 ± 6.84 | 13.23 ± 7.78 | **** | n.s. | n.s. | ** | ** | * | n.s. | n.s. | n.s. | n.s. |
Trunk’s tilt | 89.39 ± 8.79 | 86.89 ± 4.65 | 88.09 ± 5.64 | 89.59 ± 6.14 | 90.7 ± 4.21 | n.s. | n.s. | n.s. | n.s. | n.s. | n.s. | n.s. | n.s. | n.s. | n.s. |
Crown height | 23.86 ± 13.11 | 47.47 ± 21.12 | 41.04 ± 15.67 | 38.34 ± 16.47 | 72.46 ± 39.22 | **** | **** | **** | **** | **** | **** | **** | n.s. | * | n.s. |
Crown width | 34.71 ± 21.86 | 75.11 ± 39.53 | 64.8 ± 26.58 | 56.48 ± 25.54 | 95.91 ± 41.22 | **** | ** | **** | **** | **** | **** | **** | n.s. | ** | n.s. |
Root height | 1.59 ± 4.63 | 5.68 ± 8.7 | 4.5 ± 8.45 | 4.31 ± 7.83 | 7.42 ± 13.34 | **** | n.s. | * | ** | * | * | * | n.s. | n.s. | n.s. |
Root width | 3.53 ± 12.13 | 15.84 ± 23.13 | 9.41 ± 16.48 | 9.33 ± 16.89 | 18.44 ± 32.19 | **** | n.s. | ** | **** | ** | n.s. | ** | n.s. | n.s. | n.s. |
Examples of trees drawn by AD ((a) and (b)) and MCI (c) patients and controls (d).
♂ 74 yrs, AD
♀ 80 yrs, AD
♀ 71 yrs, MCI
♂ 72 yrs, control
The trunk-to-crown ratio of trees drawn by demented and MCI patients is greater than controls while the tree size-relative-to-page space index is significantly smaller. Furthermore, the tree size-relative-to-page space index of trees drawn by AD patients is smaller than that of the other cognitively impaired patients, demented or with MCI. The same index of trees drawn by FTD patients differs from AD and MCI but not from VD patients. The crown ratio of trees drawn by VD patients is significantly greater than controls.
Multiple linear regression model with forward variable selection includes, as independent predictors of cognitive impairment, the variables of tree height and trunk-to-crown ratio.
TDT has been analyzed in the elderly and in cognitively impaired patients [
In our sample, cognitively impaired patients draw trees smaller with respect to healthy subjects. Trees drawn by AD patients in particular are significantly smaller with respect to trees drawn by other cognitively impaired patients, demented or MCI, and by controls. With respect to controls, AD patients draw smaller poorly detailed trees with an increased trunk-to-crown ratio and a reduced tree size-relative-to-page space index, that is, with a smaller crown and with a reduced space occupation. MCI patients draw trees intermediate in size between AD patients and healthy subjects suggesting a sort of progression from mild to greater degrees of cognitive impairment. Different tree dimensions with respect to controls in AD and MCI patients are related both to an increasing of the trunk-to-crown ratio and to a reduction of the tree size-relative-to-page space index, which is to a prevalence of the trunk with respect to the crown of the tree and to a global reduced space occupation. FTD patients differ from AD and MCI for the tree size-relative-to-page space index: they draw, in fact, trees bigger than AD and MCI patients but smaller than controls. Conversely, this significant difference does not exist between FTD and VD patients.
Globally, the trunk-to-crown ratio and the tree size-relative-to-page space index distinguish cognitively impaired patients, demented or not, from controls and the tree size-relative-to-page space index distinguishes also FTD patients from AD and MCI patients. Furthermore, the total tree height and the trunk-to-crown ratio are predictors of cognitive impairment in our patient sample.
The trunk-to-crown ratio is known to be inversely correlated to the development of linguistic abilities and abstract thinking during the course of the development [
In adults, TDT had been also studied in psychiatric patients (eating disorders and schizophrenia) [
So both psychiatric and cognitively impaired patients equally tend to draw smaller and bad formed trees than healthy individuals. However, some characteristics are different between the two groups such as the top-end of the trunk which is generally closed in healthy individuals and in cognitively impaired patients while it is typically opened in schizophrenics [
Our data should be further confirmed in a wider patient sample selected according to advanced criteria of Alzheimer’s disease and supported by biomarkers results and advanced neuroimaging techniques.
In conclusion, we think that TDT could be a useful tool for orienting cognitive impairment diagnosis and it could be an easy test to be administered by general practitioners and in specialized outpatient clinics. Furthermore, it could be included in extensive neuropsychological batteries exploring cognitive functions of cognitively impaired patients to attempt a possible and simple approach to the study of normal and pathological aging.
The authors declare that they have no conflict of interests.