Study populations
In this study, 56,553 individuals diagnosed with mental disorders were enrolled, with a median age of 57.00 [IQR 49.00–62.00]. Among them, 20,533 (36.31%) were male, and the majority (95.32%) had white ethnicity. The sample included 27,220 individuals diagnosed with anxiety, 1,325 with bipolar disorder, 36,582 with depression, and 1,479 with schizophrenia. Table 1 presents the demographic information. Nearly 5 controls were matched for each case. Therefore, a total of 255,867 individuals were included in the main analyses. Similar demographic statistics were observed between the case and control groups (Table 1).
Table 1
The characteristics of UK-Biobank participants with mental disorders and controls.
| Anxiety | Bipolar |
| Anxiety subjects (n = 27,220) | Controls (n = 131,941) | Bipolar subjects (n = 1,325) | Controls (n = 6,559) |
Age at baseline (years) | 57.0 [49.0, 63.0] | 57.0 [50.0, 63.0] | 55.0 [48.0, 62.0] | 55.0 [48.0, 62.0] |
Gender (male, %) | 9,220 [33.9%] | 45,193 [34.3%] | 562 [42.4%] | 2,780 [42.4%] |
Townsend deprivation index | -1.7 [-3.4, 1.3] | -1.9 [-3.5, 1.0] | -0.6 [-2.9, 2.7] | -0.9 [-2.9, 2.4] |
BMI | 27.1 [24.3, 30.6] | 26.9 [24.3, 30.2] | 27.8 [24.8, 31.6] | 27.5 [24.8, 31.0] |
Ethnicity |
White | 25,986 [95.5%] | 126,383 [95.8%] | 1,248 [94.2%] | 6,212 [94.7%] |
Asian | 325 [1.2%] | 1,482 [1.1%] | 18 [1.4%] | 77 [1.2%] |
Black | 518 [1.9%] | 2,416 [1.8%] | 21 [1.6%] | 101 [1.5%] |
Others | 391 [1.4%] | 1,660 [1.3%] | 38 [2.7%] | 169 [2.6%] |
Education (years) |
< 10 | 5,754 [21.1%] | 25,014 [19.0%] | 224 [16.9%] | 1,039 [15.8%] |
10–15 | 12,047 [44.3%] | 59,956 [45.4%] | 527 [39.8%] | 2,654 [40.5%] |
> 15 | 9,419 [34.6%] | 46,971 [35.6%] | 574 [43.3%] | 2,866 [43.7%] |
Number of individuals (years before and after diagnosis) |
-10~-5 | 9,658 [35.5%] | 46,746 [35.4%] | 354 [26.7%] | 1,760 [26.8%] |
-5 ~ 0 | 6,424 [23.6%] | 31,194 [23.6%] | 328 [24.8%] | 1,623 [24.7%] |
0 ~ 5 | 6,377 [23.4%] | 30,906 [23.4%] | 349 [26.3%] | 1,718 [26.2%] |
5 ~ 10 | 4,761 [17.5%] | 23,095 [17.5%] | 294 [22.2%] | 1,458 [22.3%] |
| Depression | Schizophrenia |
| Depression subjects (n = 36,582) | Controls (n = 168,985) | Schizophrenia subjects (n = 1,479) | Controls (n = 7,276) |
Age at baseline (years) | 56.0 [49.0, 62.0] | 56.0 [49.0, 62.0] | 56.0 [48.0, 62.0] | 56.0 [48.0, 63.0] |
Gender (male, %) | 13,649 [37.3%] | 64,678 [38.3%] | 753 [50.9%] | 3,683 [50.6%] |
Townsend deprivation index | -1.5 [-3.3, 1.7] | -1.9 [-3.4, 1.0] | 1.0 [-2.3,4.1] | 0.5 [-2.5, 3.5] |
BMI | 27.5 [24.7, 31.2] | 27.1 [24.5, 30.4] | 27.8 [24.7, 31.3] | 27.6 [24.8, 30.8] |
Ethnicity |
White | 34,907 [95.4%] | 161,820 [95.8%] | 1,310 [88.6%] | 6,494 [89.2%] |
Asian | 418 [1.1%] | 1,869 [1.1%] | 70 [4.7%] | 333 [4.6%] |
Black | 635 [1.7%] | 2,907 [1.7%] | 44 [3.0%] | 200 [2.8%] |
Others | 622 [1.7%] | 2,389 [1.4%] | 55 [3.7%] | 249 [3.4%] |
Education (years) |
< 10 | 7,734 [21.1%] | 30,396 [18.0%] | 373 [25.2%] | 1,562 [21.5%] |
10–15 | 15,950 [43.6%] | 75,843 [44.9%] | 568 [38.4%] | 3,065 [42.1%] |
> 15 | 12,898 [35.3%] | 62,746 [37.1%] | 538 [36.4%] | 2,649 [36.4%] |
Number of individuals (years preceding diagnosis) |
-10~-5 | 8,397 [23.0%] | 39,123 [23.2%] | 527 [35.6%] | 2,608 [35.8%] |
-5 ~ 0 | 6,679 [18.3%] | 30,899 [18.3%] | 374 [25.3%] | 1,834 [25.2%] |
0 ~ 5 | 12,277 [33.6%] | 56,578 [33.5%] | 275 [18.6%] | 1,364 [18.7%] |
5 ~ 10 | 9,229 [25.2%] | 42,385 [25.1%] | 303 [20.5%] | 1,470 [20.2%] |
Temporal trends of blood-based makers in mental disorders before and after clinical diagnosis
The evolutionary temporal trends of 6, 15, 10 and 47 blood-based markers identified for bipolar disorder, anxiety, schizophrenia, and depression were distinct from those of the control group. These blood-based marker were grouped into 4 to 6 clusters for different mental disorders according to their temporal trends, with sizes ranging from 1 to 15 blood-based markers (Fig. 2). Although we employed a standard linear model to identify these blood-based markers, nearly all clusters displayed non-linear temporal trends within the 10-year window before and after clinical diagnosis.
In patients with anxiety disorders, the temporal trends of cluster 1 displayed a general downward trend over time, with a reduction in the rate of slowed down after diagnosis, including measures such as white blood cell count (WBC), neutrophill percentage (NEUT-P), mean sphered cell volume (MSCV), mean reticulocyte volume (MRV), free cholesterol in small ldl (S-LDL-FC), and Urate. The temporal trends of clusters 2 and 4 revealed a U-shaped evolution that reversed around the time of clinical diagnosis. Cluster 2 encompassed mean corpuscular volume (MCV) and glycated haemoglobin (HbA1c), while cluster 4 included Triglycerides, mean corpuscular haemoglobin (MCH), aspartate amino transferase (AST), and gamma glutamyl transferase (GGT). Conversely, the temporal trends of clusters 3 presented an inverted U-shape, including markers such as immature reticulocyte fraction (IRF), IGF-1, red blood cell count (RBC), and Vitamin D. Additionally, the temporal trends of cluster 5 incorporated lymphocyte percentage (LYMP-P) and high light scatter reticulocyte count (HLR-C), which increased in the 10 years before diagnosis and did not show further increase after diagnosis. Finally, in cluster 6, the temporal trends of haemoglobin concentration (Hb) demonstrated undulating changes, while the temporal trend of free cholesterol in medium ldl (M_LDL_FC) presented an inverted U-shape.
In patients with depression, the temporal trends of cluster 1 and 5 followed an inverted U-shape, with levels peaking around 2 years after diagnosis before decreasing. This cluster included biomarkers like Cholesterol, ldl cholesterol (LDL-C), and triglycerides in ldl (IDL-TG). Additionally, cluster 5 incorporated biomarkers like Acetate, red blood cell distribution width (RDW), mean corpuscular volume (MCV), and so on, whose temporal trends also presented an inverted U-shape with levels increasing prior to diagnosis but decreasing afterwards. However, compared to cluster 1, this cluster exhibited a lower rate of change. The temporal trends of cluster 2 exhibited a general upward trend over time, with a particularly notable increase in levels prior to diagnosis. This cluster included biomarkers such as total protein, alkaline phosphatase (ALP), aspartate aminotransferase (AST), mean corpuscular haemoglobin concentration (MHCH), and lymphocyte percentage (LYMP-P). On the other hand, the temporal trends of cluster 3 displayed a downward trend, encompassing biomarkers like urate, estosterone, c-reactive protein (CPR), high light scatter reticulocyte count (HLR-C), and immature reticulocyte fraction (IRF). Finally, the temporal trends of cluster 4 and 6 continued to decrease with a fast rate before diagnosis and then increased slightly. Cluster 4 incorporated blood-based markers like NEUT-P, SHBG, WBC, and vitamin D, while cluster 6 consisted of markers such as total bilirubin, mean platelet volume (MPV), Hb, and RBC.
In patients with schizophrenia, the temporal trends of cluster 1 followed an inverted U-shape, with levels peaking around 2 years after diagnosis before decreasing. This cluster included blood markers such as Acetate and red blood cell distribution width (RDW). Conversely, the temporal trends of cluster 2 followed a U-shape, with the lowest level between 0 and 2 years after diagnosis. This cluster included markers such as Hb, haematocrit percentage (HCT), WBC, and cysytain C. The temporal trends of cluster 3 increased before diagnosis and then decreased 2–4 years after diagnosis, including measures such as ALP, CPR, MSCV, and MRV. On the other hand, the temporal trends of cluster 4 demonstrated an inverted U-shape over time between − 10 and 4 years, including factors such as HbA1c and GGT. Finally, the temporal trends of Cluster 5 exhibited a downward trend, encompassing only Vitamin D.
In patients with bipolar disorder, the temporal trends of biomarkers can be categorized into four distinct clusters. Cluster 1 comprises markers such as RBC, Hb, Hct, and IRF, which follow a U-shaped temporal trends with the lowest values occurring around the diagnosis date. Cluster 2 incorporates markers of MCV and MSCV, whose temporal trends exhibit a downward trend. On the other hand, cluster 3 comprises a single blood marker, high light scatter reticulocyte percentage (HLR-P), which follows an upward temporal trends.
Identified blood-based makers were associated with brain structures
We found significant positive relationships between markers linked to lipid metabolism—specifically, cholesterol and LDL-C levels—and the volume of numerous cortical brain regions. Additionally, immune markers such as neutrophill count (NEUT-C), lymphocyte count (LYMP-C), and CPR were found to be correlated with the volume of several brain regions, including the orbitofrontal cortex and hippocampus. Notably, the level of vitamin D in the blood was positively correlated with the volume of the medial orbitofrontal cortex. Furthermore, an elevation in WBC was associated with a reduction in the volume of orbitofrontal and hippocampus regions, as well as an increase in ventricular volume (Fig. 3A).
Additionally, we found significant relationships between the MD values of the uncinate fasciculus (UF), superior thalamic radiation (STR), and superior longitudinal fasciculus (SLF) and most blood-based markers (Fig. 3). The ICVF values of the parahippocampal part of cingulum (PPOC), middle cerebellar peduncle (MCP), and corticospinal tract were associated with certain blood cell counts, including red and white blood cell counts, hemoglobin concentration, haematocrit percentage, NEUT-C and LYMP-C. Furthermore, liver function markers such as ALP and ALT, as well as vitamin D levels, were also linked to these brain structures. Notably, the FA values of the MCP and forceps major were found to be associated with lipid metabolism indicators, immune markers, and liver function markers, including triglycerides, CRP, and GGT (Fig. 3B).